Note: Descriptions are shown in the official language in which they were submitted.
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Therapeutic Foam
[001]
[002] The present invention relates to the generation of foam
comprising a sclerosing material, particularly a sclerosing solution, which is
suitable for use in the treatment of various medical conditions involving
blood
vessels, particularly varicose veins and other disorders involving venous
malformation.
[003] Sclerosis of varicose veins is based on the injection into the
veins of liquid sclerosant substances which, by inter alia causing a localised
inflammatory reaction, favour the elimination of these abnormal veins. Until
recently, scierotherapy was a technique selected in cases of small and
medium calibre varicose veins, those with diameters equal to or greater than
7 mm being treated by surgery.
[004] An injectable microfoam suitable for therapeutic use, on larger
veins in particular, has now been developed and is described in
EP-A-0656203 and US 5676962 (Cabrera & Cabrera).
These describe a low-density microfoam produced with a
sclerosing substance which, when injected into a vein, displaces blood and
ensures that the sclerosing agent contacts the endothelium of the vessel in a
known concentration and for a controllable time, achieving sclerosis of the
entire segment occupied.
[005] Prior to the priority date of these patents it had been known for
many years that injection of liquid sclerosant into varicose veins, especially
smaller varicose veins, could be effective. It had also been known for many
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years to inject a small quantity of air into a vein prior to injecting
sclerosing
liquid, the objective being to displace blood from the vein to avoid the
sclerosing agent being diluted too quickly. A development of this technique
was to make a loose foam or froth and to inject this instead of pure air,
prior
to injection of the sclerosant liquid. These techniques, known as "air block"
and developed by Orbach, were generally only effective for treating smaller
veins.
[006] In addition there had been disclosures of finer foams for
treatment of smaller varicose veins (Fluckiger references cited below), or a
combined procedure using both surgery and foam for treatment of the entire
long saphenous vein: Mayer; Brucke: "The Aetiology and Treatment of
Varicosities of the Lower Extremities" Chirurgische Praxis, 521-528, 1957.
[007] All of these prior disclosures of foam/froth treatment describe
the preparation of the foam/froth with air as the gaseous component. None of
the documents mentions the air in the injected foam giving rise to serious
problems. One reference mentions an apparently short lived air embolism:
P.Fluckiger:"Non-surgical retrograde sclerosis of varicose veins with Varsyl
foam'; Schweizerische Medizinische Wochenschrift No.48, pp1368-1370
(1956). In this article, the author indicates that he reduced the volume of
foam administered to 10ml from 15m1 as a result of a patient experiencing
chest pain on standing immediately after treatment with 15ml of foam. In a
later lecture, the same author indicates that he has in fact subsequently used
15m1 foam without noting ill effects: lecture dated 1962 entitled "A
contribution
to techniques for outpatient treatment of varicose veins" delivered to the
Hamburg Dermatological Society. The reference by Mayer and Brucke cited
above appears to describe the use of as much as 50m1 of air foam and does
not mention any problems.
[008] However, it is known that rapid intravenous injection of a large
quantity of air, as opposed to air foam, can lead to air embolism which may
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be fatal. In spite of this practitioners of the air block and foam techniques
described above do not report that the volumes of air involved in their
techniques were sufficient to cause serious problems.
[009] The air block technique had largely fallen out of favour by the
1980s and the other foam techniques mentioned above were virtually
unheard-of.
[010] The Cabreras proposed the use of a microfoam, that is to say a
microfoam with microscopically small bubbles, e.g., where the majority of the
bubbles are not visible to the naked eye, for injection into varicose veins.
The
use of a microfoam, as opposed to larger bubbled foam or froth, gives rise to
many advantages in terms of controllability and ability to displace blood in
even the largest varicose veins, allowing treatment of virtually all varicose
veins without recourse to surgery. As used here, the term foam
encompasses foams with bubbles of all sizes including microfoams.
[011] The first teaching that potential issues with intravenous injection
of a microfoam product made with air are serious enough to warrant change
is to be found in the Cabrera patent references mentioned above. These
documents indicate that the prior air based techniques are "dangerous owing
to the side effects of atmospheric nitrogen which is only slightly soluble in
blood", though it is not mentioned exactly what the dangers are nor what
volumes or rates of injection of air or nitrogen gas give rise to these
dangers.
[012] In addition to being the first to propose a microfoam as opposed
to a larger bubbled foam, and to propose treatment of even the largest veins
without surgery, the Cabreras also proposed that the microfoam be made with
oxygen or a mixture of carbon dioxide and oxygen. In the context of this
background, the Cabreras' contribution can be seen to be highly innovative in
a number of respects - appreciating against the prevailing thinking at the
time
(i) the potential of a sclerosant microfoam, (ii) the need for soluble gases,
(iii)
the use of oxygen which does not degrade the microfoam yet is taken up by
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blood, (iv) the safety of oxygen but also (v) the possibility of incorporating
a
percentage of highly soluble carbon dioxide.
[013] Since publication of the Cabreras' microfoam technique in the
mid 1990s many practitioners have adopted foam both in Europe and the
USA. At the recent worldwide conference of phlebologists in San Diego in
August 2003, approximately one third of the two hundred and fifty or so
papers which were presented concerned foam treatment.
[014] Almost without exception, however, practitioners using
sclerosing foam today make it with air. Opinion varies as to how much foam
should be injected - some advocate as little as 5m1 whilst others are prepared
to inject more.
[015] The Cabreras' microfoam is prepared extemporaneously in the
clinic immediately prior to use. The preparation involves beating sclerosant
solution with a small brush rotated at high speed by a motor, under a cover
which is connected to a source of oxygen or oxygen and carbon dioxide.
Most practitioners who have followed the Cabreras use an alternative
technique for extemporaneous preparation of foam which involves passing
sclerosant solution and air repeatedly between two connected syringes.
Another alternative is a syringe with a second plunger with holes in its face
and which is independently movable in the syringe barrel to froth a liquid and
gas mixture in the syringe. Both of these latter types of procedure are
somewhat inconvenient and allow for variation of the foam composition
depending upon the person preparing it: gas content, bubble size, density and
stability all require attention. These techniques require a high degree of
care
and knowledge that may be difficult to replicate under pressure, i.e. when
time available to prepare the foam is short.
[016] A product which aims essentially to reproduce the Cabreras'
microfoam in a more convenient and easily reproducible way is currently
being developed and is in clinical trials in Europe and the USA. This product
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is a pressurised canister system, in which the foam is produced by passing
gas and sclerosant solution under pressure through a number of fine meshes.
In the trials of this product the aim is to treat an entire long saphenous
vein
and its varicosed tributaries in a single treatment, which can mean injection
of
25m1 or even 50ml of foam.
[017] WO 00/72821-Al (BTG International Limited)
describes the fundamental concepts underlying this
canister product. The foam is produced by passing gas and sclerosant liquid
through one or more meshes having small apertures measured in microns.
Like the Cabrera patents, this document acknowledges the potential issues
with air / nitrogen and seeks to reduce the levels of nitrogen in the foam. A
preferred form of gas described in WO 00/72821-A1 comprises 50% vol/vol or
more oxygen, the remainder being carbon dioxide, or carbon dioxide, nitrogen
and trace gases in the proportion found in atmospheric air.
[018] In a later patent application, WO 02/41872-Al
(BTG International Limited) the sclerosant liquid
and an oxygen-rich physiologically acceptable blood dispersible gas are
stored in separate containers until immediately prior to use, when the blood-
dispersible gas is introduced into the container holding the sclerosant
liquid.
The mixture of blood-dispersible gas and sclerosant liquid is then released,
the components of the mixture interacting upon release of the mixture to form
a sclerosing foam. In the system described in this patent application, a
proportion of nitrogen (25%) is deliberately introduced into the polidocanol
canister. After charging of the sclerosing liquid (polidocanol) can with
oxygen
from the higher pressure oxygen canister, the percentage of nitrogen is
reduced to about 7 or 8%. It was believed that this level of nitrogen could be
tolerated.
[019] The device disclosed in WO 02/41872-Al gives a good uniform
injectable foam, irrespective of the gases used. Use of 100% CO2 as the
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filling gas in the polidocanol canister is preferred, as CO2 is very soluble
in the
bloodstream, but the present inventors have observed that increasing CO2
percentage in the final gas mix may cause an undesirable decrease in foam
stability, resulting in a shorter half separation time. In particular, the
half-life of
the foam can fall short of the figure of 2.5 minutes which is indicated in
WO 00/72821-Al as being preferable.
[020] The present inventors are continuing to research clinical
aspects of the injection of sclerosing foam as well as developing the canister
foam product and putting it through clinical trials in Europe and the USA. It
has always been the intention to develop a safe foam product which is as well
defined as possible but whose specification has achievable tolerances. There
are many parameters of a foam which may be varied. These include, without
limitation: the chemical, its purity and the strength of the solution; the
size of
bubbles, or more accurately the distribution of sizes, the density (i.e. ratio
of
liquid to gas), the longevity of the foam (measured in terms of "half life",
or the
time taken for half the foam to revert to liquid) and the gas mixture.
[021] Nitrogen, which makes up approximately 80% of air, is difficult
as a practical matter to exclude totally from a foam. This is true whether the
foam is made using a canister system, in which case nitrogen tends to creep
into the canister during manufacture, or using either of the syringe
techniques
or the Cabreras' rotating brush technique, or indeed any of a number of other
less common techniques which have been developed since the Cabreras'
disclosure of microfoam.
[022] In a two syringe technique the likely method for introducing the
gas component, if a foam were to be made with a gas other then air, would be
to connect one syringe to a pressurised source of gas, then disconnect and
reconnect it to another syringe containing sclerosant. In this sort of
technique, the two syringes are pumped to create foam and then the foam-
filled syringe separated. The potential for ingress of a small percentage of
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air/nitrogen during this process is obvious. Similarly, even with the
Cabreras'
technique, it may be difficult to exclude 100% of air/nitrogen from the
environment in which the foam is prepared.
[023] One of the objectives of the foam product being developed by
the inventors is to treat an entire greater saphenous vein together with major
varicose tributaries in a human patient with one injection. This requires up
to
25m1, 30m1 or possibly even 50ml of foam. Currently, the most conservative
users of air foam inject a maximum of 5m1 into the venous system, apparently
without observing any deleterious effects. The inventors therefore reasoned
that an equivalent amount of nitrogen in a relatively large dose of foam
needed to treat the entire saphenous vein should also be safe. They
therefore used this as a starting point: 5m1 of air with 80% nitrogen will
contain 4m1 nitrogen; a corresponding proportion of nitrogen in, say, 50ml of
low nitrogen foam would be around 8%.
[024] Until recently, its has been believed by the inventors that a foam
with approximately 8% nitrogen would be acceptable from a safety standpoint
and that this percentage represented an easily achievable tolerance for
nitrogen levels in the foam specification. Accepting this level of nitrogen
also
has the advantage that a small quantity of nitrogen could be introduced
deliberately into the polidocanol canister to reduce the adverse effects of
the
highly soluble carbon dioxide on the foam stability (as discussed above). This
foam and a system for making it is described in WO 02/41872-Al, referred to
above.
[025] As discussed above, apart from the above mentioned patent
publications, the published art on foam treatment of varicose veins mentions
little if any danger from injecting air foam up to 15m1. The only event noted
by
Fluckiger was temporary chest pain. The above mentioned patent
publications which mention dangers with nitrogen are silent regarding the
amount of nitrogen which would be dangerous and what damaging effects it
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may cause. A great many practitioners are currently using air based foam,
though some restrict the quantity injected to 5ml. The inventors have been
involved in a 650 patient multi-centre European phase III clinical trial of
the
canister product described above which contains 7-8% nitrogen; no serious
adverse events associated with the gas component of the foam were noted.
[026] Now, further research in connection with the clinical trials of the
canister system described above has revealed the presence of large numbers
of bubbles in the heart, some of which endure for a significant period of
time.
Ultrasound monitoring of the heart during treatment of patients in this trial
has
revealed many bubbles on the right side of the heart and in associated blood
vessels. Since foam is injected into the venous circulation, i.e. that
connected
to the right side of the heart, it was expected that some bubbles on the right
side of the heart would be observed. However, the number and persistence
of the bubbles was surprising.
[027] Furthermore, bubbles have been observed on the left side of the
heart in a patient who was subsequently shown to have a minor septal defect,
or patient foramen ovale ("PFO"), i.e. a hole in the heart. The patient
reported
experiencing a transient visual disturbance. This is significant because, once
on the left side of the circulation, the bubbles can progress to the brain,
where
they may cause microinfarcts.
[028] At present it is believed that screening all patients for even the
most minor PFO is not really feasible for an elective procedure such as
varicose vein treatment and may not even be possible. The techniques
required would be fairly sophisticated and possibly quite invasive.
Furthermore this would increase the time required for the procedure and
preclude treatment of patients having such PFOs, of which it is believed there
are significant numbers.
[029] In the light of these unexpected findings, considerable further
fundamental research has been carried out by the inventors.
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Experiments using animal models have been carried out by the
inventors and internationally recognised experts in their field have been
commissioned to carry out detailed mathematical modelling of the behaviour
of oxygen, carbon dioxide and nitrogen bubbles in blood. In vitro work to
measure the absorption of gases in fresh human venous blood has also been
carried out by the inventors. As a result it has become clear that, contrary
to
previous thinking by the inventors, and in stark contrast to the thinking of
almost every practitioner currently preparing extemporaneous foam for use in
varicose vein treatment, even the smallest volume of nitrogen may be
significant in causing persistent bubbles.
[030] Furthermore, recent studies have been published further
confirming that air foams previously suggested in the art are causing some
complications for certain patient groups. For example, Dr. Philip Kritzinger,
MD has presented case studies where foams for sclerotherapy of veins that
were made using air as the gas phase may lead to seizures and myocardial
infarction in some geriatrics or patients at high risk of coronary problems.
[031] The inventors have now determined that in order to produce a
product suitable for administration to patients without the need for lengthy
PFO screening methodology it may be required to reduce the amount of
nitrogen to upper limits that were previously unrecognised.
[032] Further developments of the canister system described in
W000/72821-A1 and W002/41872-A1 have been devised, specifically raising
the percentage of carbon dioxide in the foam and reducing the nitrogen
present in the foam to near zero. To compensate for the deleterious effects
of the highly soluble carbon dioxide, the size of the apertures in the mesh
has
been reduced to 5 microns from 20 microns. Canisters of this design have
been made in reasonably large numbers for testing. Initially, double canister
systems as described above were prepared by flushing the canisters with the
desired gas before sealing and pressurising them. This product generated a
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foam with between 1 % and 2% nitrogen. Further research has led the
inventors to believe, however, that even this level may be too high.
[033] Recognising that there will always be impurity no matter what
technique is adopted for making the foam, the inventors believe that a
sclerosing foam having a percentage by volume of nitrogen gas within the
range 0.01 % and 0.8% is both clinically safe and consistently reproducible.
It
may be possible routinely to produce canisters with as little as 0.0001 %
nitrogen gas. Examples presented below illustrate the
manufacture/preparation and also the clinical effects of such a foam.
[034] The inventors also recognise that techniques such as those
described above using syringes, together with a variety of other techniques
for extemporaneous preparation of sclerosing foam which have been
developed since the Cabreras disclosure, may have their place in the field of
foam scleropathy. These techniques may well provide a less expensive
option than a canister product. The inventors believe that it is possible to
prepare foams having a very low percentage of nitrogen, as set out above,
using these types of technique as well as using a canister system.
[035] According to the present invention, a foam comprising a liquid
phase and a gas phase wherein the liquid phase comprises at least one
sclerosing agent and the gas phase consisting essentially of gaseous
nitrogen present in an amount ranging from 0.0001 % to 0.8% by volume and
at least one physiologically acceptable gas. In a further embodiment, the gas
phase may further comprise other gases such as trace gases as defined
below, which may also effect at least one of at least one of the density, half
life, viscosity, and bubble size of the resulting foam. As used herein,
consisting essentially of means that one or more additional component may
be added, such as gas, that would not substantially effect at least one of the
density, half life, viscosity, and bubble size of the resulting foam.
[036] "Physiologically acceptable gas" means gases which are
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relatively readily absorbed by the blood or which can pass rapidly across the
pulmonary gas exchange membranes. Specifically, oxygen, carbon dioxide,
nitrous oxide and helium are contemplated. Other gases, which may or may
not fall within the terms of the definition of physiologically acceptable
gases,
may be used at least in small quantities, e.g. xenon, argon, neon or others.
As used herein, a gas phase that is "substantially" a specific gas, such as
"substantially 02", refers to a gas phase that is 02 with the impurities
normally found in commercial medical grade 02 gas. Gases which are found
only at trace concentrations in the atmosphere (such as those just mentioned)
may be useful to incorporate in the formulation, e.g. at relatively low
concentrations of between about 0.1 % and 5%, in order to facilitate the
detection of leaks.
[037] In another embodiment, the said other gas consists essentially
of oxygen. Another possibility is for the other gas to consist essentially of
oxygen and a minor proportion, preferably 40% or less of carbon dioxide, still
more preferably 30% or less of carbon dioxide. For example, the gas phase
may comprise at least 50% 02, such as for example, as 70%, 80%, 90% and
99% 02. In another embodiment, it may also comprise a major portion of
C02, such great than 50% C02, such as 70%, 80%, 90% and 99% C02. In
these cases, between 0.1 % and 5% of the other gas may be constituted by
gases which are only found at trace levels in the atmosphere, e.g. argon,
helium, xenon, neon. Alternatively the gas may be substantially 100% nitrous
oxide or a mixture of at least two of oxygen, nitrous oxide and carbon
dioxide.
[038] For the purpose of this application various other terms have the
following definitions: A sclerosant liquid is a liquid that is capable of
sclerosing
blood vessels when injected into the vessel lumen and includes without
limitation solutions of polidocanol, tetradecyl sulphate, ethanolamine oleate,
sodium morrhuate, hypertonic glucosated or glucosaline solutions, chromated
glycerol, iodated solutions. Scleropathy or sclerotherapy relates to the
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treatment of blood vessels to eliminate them. An aerosol is a dispersion of
liquid in gas. A major proportion of a gas is over 50% volume/volume. A minor
proportion of a gas is under 50% volume/volume. A minor amount of one
liquid in another liquid is under 50% of the total volume. Atmospheric
pressure and bar are 1000 mbar gauge. Half-life of a foam is the time taken
for half the liquid in the foam to revert to unfoamed liquid phase.
[039] As suggested by Cabrerra and discussed above, one could use
oxygen or mixtures of oxygen and carbon dioxide of the gas component.
Carbon dioxide is very soluble in water (and hence blood) and oxygen is not
very soluble in water but is taken up relatively rapidly by haemoglobin in
blood. The present inventors have also done studies that have shown that
C02 and 02 are taken up in blood much faster than N2 or air. However,
foams made solely with carbon dioxide, or other highly water-soluble gases,
tend to be very unstable and do not last long enough to be usable. Because
C02 foams have a very short half life, foams with a high concentration of
C02 have not been used in the past to prepare foams for scelrotherapy.
[040] For example, a predominantly insoluble gas mix such as air will
yield a stable, stiff foam with a half separation time of 150-200 seconds
using
the Cabrera method. However, highly soluble gas atmospheres such as
100% C02 yield foams with much shorter half separation times. It is thought
that the rapid dissolution and transport of C02 in the lamellar cell walls of
the
foam is responsible for the reduced stability of some C02 foams. This allows
the smaller, high pressure bubbles of the foam to rapidly transfer all their
gas
content to adjacent larger low pressure bubbles, which then rise through the
foam to burst or accumulate at a surface. This process is called Ostwalt
ripening, and with all-C02 foams the liquid cell wall is no longer a
significant
barrier to diffusion between adjacent bubbles at different Laplace pressures.
Drainage and separation of foam into gas and liquid components is also
influenced by the viscosity of the liquid component.
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[041] Oxygen foams do not have this problem, but the injection of
oxygen gas has been reported to be dangerous and, in fact, has been said to
be almost as dangerous as air when injected into the venous system. See,
for example, Moore & Braselton "Injections of Air and carbon Dioxide into a
Pulmonary Vein" Annals of Surgery, Vol 112, 1940, pp 212-218. While
another study suggests that for some high risk patient groups high
concentrations of 02 in foams used for sclerotherapy may increase the risk of
side effects.
[042] Recent studies have also suggested that foams for
sclerotherapy made with high concentrations of N2 or 02 may lead to
potential side effects in certain patient groups. More specifically, one study
suggests that high concentrations of nitrogen may lead to a higher risk of
arterial embolism in certain patient populations.
[043] The present inventors, however, have discovered that it is
possible to make an effective foam for use in sclerotherapy using high
concentrations of C02 as the gas phase and the addition of a viscosity
enhancing agent to the liquid phase. The addition of a viscosity enhancing
agent, however, while increasing the half life of a C02 foam, also increases
the density of the foam. Too high of a density can hinder a foams ability to
displace blood and therefore be an effective foam for sclerotherapy. It was
discovered that a balance of density and half life enables the production of
an
effective foam. In one embodiment, this balance of density and half life is
achieved by increasing the viscosity enhancing agent to at least 20% wt/wt
and using various methods as described herein to produce the foam.
[044] Viscosity enhancing agents include any agent that will increase
the viscosity of the liquid phase, such as PVP and glycerol. In one
embodiment, at least 20% wt/wt viscosity enhancing agent is present in the
liquid phase, such as for example 25%, 30%, 35%, 40%.
[045] Viscosity of the liquid phase before production of the foam may
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also be a factor in the half life of the foam. For example, increasing
viscosity
of the liquid phase will increase half life of the foam. However, a higher
viscosity may raise the density of the resulting foam in some systems.
[046] Thus, in a further embodiment, the foam of the invention
comprises a liquid phase and a gas phase wherein the liquid phase
comprises at least one sclerosing agent and is at least 20% wt/wt of at least
one viscosity enhancing agent; and the gas phase comprises at least 50%
C02; and wherein the foam has a density less than 0.25 g/cm and half life of
greater than 100 secs. The gas phase may, for example be at least 75%
C02, such as at least 90% C02, such as at least 99% C02. In one
embodiment, the gas phase consists essentially of C02.
[047] The foam, for example, may have a half life of at least 90
second, such as at least 100, such as at least 110, such as at least 120
seconds, such as at least 130 seconds, such as at least 140 seconds, such
as at least 150 seconds, such as at least 160 seconds, such as at least 170
seconds, such as at least 180 seconds, and such as at least 3.5 minutes.
The density of the foam may range from 0.07 to 0.22, such as 0.07 to 0.19
g/ml, 0.07 to 0.16 g/ml, such as 0.08 to 0.14, also such as 0.8 to 0.15 g/ml,
such as 0.9 to 0.13 g/ml and such as 0.10 to 0.14 g/ml. The gas phase may
further comprises another physiologically acceptable gas that is dispersible
in
blood, such as 02. The viscosity of the liquid phase may range from 2.0 to
10 cP, such 2.0 to 7.0 cP, such as 2.0 to 5.0 cP, such as 2.0 to 3.5 cP, such
as from 2.0 to 3.0 cP, such as 2.0 to 2.5 cP.
[048] FIGURES
[049] Figure 1 is a schematic representation of a syringe barrel part of
a first embodiment of device in accordance with the first aspect of the
invention, showing it in a sealed state for storage;
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[050] Figure 2 is a schematic representation of a cartridge for use with
the syringe barrel of Figure 1;
[051] Figure 3 is a schematic representation of a modified cartridge
for use with the syringe barrel of Figure 1;
[052] Figure 4 is a further schematic representation of the syringe
barrel of Figure 1 with a cartridge of the type shown in Figure 3 being
installed;
[053] Figure 5 is a further schematic representation of the syringe
barrel of Figure 1 with a foaming unit and plunger stem fitted;
[054] Figure 6 is a schematic representation of the syringe, cartridge
and foaming device of Figure 5, with the plunger stem of the syringe partially
depressed;
[055] Figure 7 is a schematic representation of a second embodiment
of device in accordance with the first aspect of the invention, comprising
charged syringe with foaming unit fitted;
[056] Figure 8 is a schematic representation of the device of Figure 7
installed in a syringe driver for generation and delivery of foam at a
controlled
rate;
[057] Figure 9 is a schematic representation of a third embodiment of
device according to the invention;
[058] Figure 10 is a schematic representation of the device of Figure
9 fitted to a motorized driver;
[059] Figure 11 is a plan view of a mesh element of an embodiment of
a foaming unit forming part of the invention;
[060] Figure 12 is a side sectional view along the line I-I in Figure 11;
and
[061] Figure 13 is a side sectional view of an embodiment of foaming
unit forming part of the invention.
[062] Figure 14 shows a cross-sectional view of a pre-pressurised
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container for the generation of therapeutic foam according to the invention,
as
disclosed in WO 00/72821-A1 and further described below.
[063] Figure 15 shows a shows a cross-sectional view of a device
comprising a container provided with engaging means and a mesh stack
shuttle according to the invention, as disclosed in WO 02/41872-Al and
further described in below.
[064] Figure 16 shows a graph to compare the results from the four
bi-can conditions tested in Example 3 below, showing the effect of gas mix,
gas pressure and shuttle mesh on foam density and half-life. Control 1 uses a
75% C02/25% N2 gas mixture in a 0.5 bar canister with a 5 m mesh; Test 1
uses the same gas mixture with a 5 pm mesh; Control 2 uses 100% C02 in a
1.2 bar canister with the 20 pm mesh; Test 2 uses the same gas with a 5 m
mesh.
[065] Figure 17 shows a graph of the average number of bubbles by
diameter from the four bi-can conditions tested below.
[066] Figure 18 shows a graph of the proportion of bubbles by
diameter from the four bi-can conditions tested in below.
[067] Figure 19 shows a graph of the average volume of bubbles by
diameter from the four bi-can conditions tested in below.
[068] Figure 20 shows a graph of the proportion of bubbles by
diameter from the four bi-can conditions tested in below.
[069] Figure 21 shows a graph to compare the results from the four
bi-can conditions tested below, showing the effect of shuttle mesh size on
half-separation time and density.
[070] Figure 22 shows the effects of (a)glycerol concentration on
viscosity of the liquid phase before mixing with the gas phase to form a foam
and (b) the effects of various viscosity enhancing agents on viscosity of the
liquid phase.
[071] Figure 23 (a, b, and c) shows the effects of various viscosity
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enhancing agents on the density and half life of a Cabrerra foam.
[072] Detailed Description
[073] For the purpose of this application terms have the following
definitions: A sclerosant liquid is a liquid that is capable of sclerosing
blood
vessels when injected into the vessel lumen. Scleropathy or sclerotherapy
relates to the treatment of blood vessels to eliminate them. An aerosol is a
dispersion of liquid in gas. A major proportion of a gas is over 50%
= 10 volume/volume. A minor proportion of a gas is under 50% volume/volume A
minor amount of one liquid in another liquid is under 50% of the total volume.
Atmospheric pressure and bar are 1000 mbar gauge. Half-life of a foam is the
time taken for half the liquid in the foam to revert to unfoamed liquid phase.
[074] In one embodiment, the foam is such that 50% or more by
number of its gas bubbles of 25 m diameter and over are no more than
200 m diameter.
[075] Half-life is conveniently measured by filling vessel with a known
volume and weight of foam and allowing liquid from this to drain into a
graduated vessel, the amount drained in a given time allowing calculation of
half-life i.e. of conversion of foam back into its component liquid and gas
phases. This is preferably carried out at standard temperature and pressure,
but in practice ambient clinic or laboratory conditions will suffice.
[076] As used here, the viscosity is determined by Brookfield
DVII+Pro made by Brookfield Engineering Labs at room temperature.
[077] In one embodiment, the gas/liquid ratio in the mix is controlled
such that the density of the foam is 0.09 g/mL to 0.16 g/mL, more preferably
0.11 g/mL to 0.14 g/mL.
[078] In another embodiment, the foam has a half-life of at least 100
seconds, such as for example, 2 minutes, 2.5 minutes, and 3 minutes. The
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half-life may be as high as 1 or 2 hours or more, but is preferably less than
60
minutes, more preferably less than 15 minutes and most preferably less than
minutes.
[079] In one embodiment, the mixture of gas and sclerosant liquid is
5 in the form of an aerosol, a dispersion of bubbles in liquid or a macrofoam.
By
macrofoam is meant a foam that has gas bubbles that are measured in
millimetres largest dimension, e.g. approximately 1 mm and over, and over
such as can be produced by lightly agitating the two phases by shaking. In
another embodiment, the gas and liquid are provided in the form of an aerosol
10 where a source of pressurized gas and a means for mixing the two is
provided to the point of use. It may be that a macrofoam is first produced
where the liquid and gas are brought together only at the point of use.
[080] The ratio of gas to liquid used in the mixture may be important in
order to control the structure of the foam produced such that its stability is
optimized for the procedure and the circumstances in which it is being carried
out. For some foams, one may mix 1 gram sclerosant liquid with from
approximately 6.25 to 14.3 volumes (STP), more preferably 7 to 12 volumes
(STP), of gas.
[081] In one embodiment, the physiologically acceptable blood
dispersible gas comprises a major proportion of carbon dioxide and/or
oxygen. In some embodiments, the foam may comprise a minor proportion of
nitrogen. While a proportion of nitrogen may be present, as in air, the
present
invention provides for use of carbon dioxide and/or oxygen without presence
of nitrogen.
[082] In one form the gas used is a mixture of carbon dioxide and
other physiological gases, particularly containing 3% vol/vol or more carbon
dioxide, such as from 10 to 90% carbon dioxide, such as from 30 to 50%
carbon dioxide. The other components of this gas may be oxygen.
[083] Another form of gas comprises 50% vol/vol or more oxygen, the
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remainder being carbon dioxide, or carbon dioxide, nitrogen and trace gases
in the proportion found in atmospheric air. One gas is 60 to 90% vol/vol
oxygen and 40 to 10% vol/vol carbon dioxide, another is 70 to 80% vol/vol
oxygen and 30 to 20% vol/vol carbon dioxide. One embodiment is 99% or
more oxygen.
[084] Preferably the sclerosing agent is a solution of polidocanol or
sodium tetradecylsulfate in an aqueous carrier, e.g. water, particularly in a
saline. More preferably the solution is from 0.5 to 5% v/v polidocanol,
preferably in sterile water or a physiologically acceptable saline, e.g. in
0.5 to
1.5% v/v saline. Concentration of sclerosant in the solution will be
advantageously increased for certain abnormalities such as Klippel-
Trenaunay syndrome.
[085] Polidocanol is a mixture of monolauryl ethers of macrogols of
formula C12C25(OCH2CH2)nOH with an average value of n of 9. It will be
realized that mixtures with other alkyl chains, oxyalkyl repeat units and/or
average values of n might also be used, e.g. 7 to 11, but that 9 is most
conveniently obtainable, e.g. from Kreussler, Germany, e.g. as
AethoxysklerolTM, a dilute buffered solution of polidocanol.
[086] The concentration of sclerosant in the aqueous liquid is a 1-3%
vol/vol solution, such as polidocanol, in water or saline, such as about 1 %
vol/vol. The water or saline also, in some cases at least, contain 2-4%
vol/vol
physiologically acceptable alcohol, e.g. ethanol. Saline may be buffered.
Some buffered saline is phosphate buffered saline. The pH of the buffer may
be adjusted to be physiological, e.g. from pH 6.0 to pH 8.0, more preferably
about pH 7Ø
[087] The sclerosant may also contain additional components, such
as stabilizing agents, e.g. foam stabilizing agents, e.g. such as glycerol.
Further components may include alcohols such as ethanol.
[088] In one embodiment, ranges for the gaseous nitrogen volume at
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are 0.0001 % to 0.75%, such as 0.7%, such as 0.6%, and such as 0.5%.
Although from a theoretical viewpoint it may be desirable to eliminate as
much nitrogen as possible, it is also understood that since we live in an
atmosphere of 80% nitrogen there are difficulties in consistently making a
foam with a very high degree of purity with regard to nitrogen gas.
Accordingly, the lower end for the range of nitrogen impurity which is
preferable (from the point of view of being easier and/or less expensive to
manufacture) is 0.0005%, more preferably 0.001 %, still more preferably
0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3% or 0.4%. As will be apparent from
the examples below, each incremental increase in the lower end of the range
may result in a purifying step being taken out of the manufacturing procedure,
with resulting cost savings.
[089] Also according to the invention is provided a canister system
adapted to dispense a foam and whose contents consist of a liquid phase and
a gas phase, wherein the liquid phase comprises a sclerosing agent and the
gas phase consists of a minor proportion of nitrogen gas and a major
proportion of other gas, preferably physiologically acceptable gas, such that
the gas phase of a foam produced by the canister system consists of between
0.0001 % and 0.8% nitrogen gas. The other possible ranges for the nitrogen
gas component, as recited above, also apply.
[090] It will be appreciated that the term "canister system" can mean
either a single canister containing a liquid and a gas for dispensing to
generate a foam, or a two canister arrangement as described above, where
gas is stored in one canister and liquid, optionally together with gas, in
another.
[091] In one embodiment, said minor proportion of nitrogen gas in the
canister is also 0.0001% to 0.8% by volume of the total gas volume in the
canister, or optionally the other ranges recited above.
[092] In another embodiment, the canister includes an element
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through which the liquid and gas contents pass in order to dispense foam. In
one embodiment, this element has apertures of approximately 0.1 to
15micron diameter, more preferably 1-7micron, still more preferably about
5micron.
[093] Another aspect of the present invention is a method for
producing a foam suitable for use in scleropathy of blood vessels,
particularly
veins, characterized in that it comprises passing a mixture of gas and an
aqueous sclerosant liquid through one or more passages having at least one
cross-sectional dimension of from 0.1 to 15 m, the ratio of gas to liquid
being
controlled such that a foam is produced having a density of between
0.07 g/mL to 0.19 g/mL and a half-life of at least 100 seconds, such as 2
minutes, such as 2.5 minutes.
[094] Preferably, the said one or more passages have at least one
cross-sectional dimension of from 1-7 micron, more preferably about 5
micron.
[095] In accordance with the original specification (as set out in
W000/72821-A1), the foam is preferably such that 50% or more by number of
its gas bubbles of 25 m diameter and over are no more than 200 m
diameter. Again in accordance with the original specification in
W000/72821-A1, preferably the method provides a foam characterised in that
at least 50% by number of its gas bubbles of 25 pm diameter and over are of
no more than 150 pm diameter. More preferably at least 95% of these gas
bubbles by number are of no more than 280 pm diameter. Still more
preferably at least 50% by number of these gas bubbles are of no more than
130 pm diameter and still more preferably at least 95% of these gas bubbles
by number are of no more than 250 pm diameter.
[096] In one embodiment, the gas comprises from 1% to 50% carbon
dioxide, preferably from 10% to 40%, more preferably from 20% to 30%.
Surprisingly, it has been found that by using a smaller aperture size for the
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mesh, foams having the specification set out in W000/72821-A1 can be
made with gas mixtures having higher proportions of carbon dioxide and
correspondingly lower proportions of insoluble gases such as nitrogen.
Carbon dioxide may be a desirable component of the gas mixture due to its
extreme solubility, greater than that of oxygen.
[097] Also according to the invention a method for angiologic
treatment comprises injecting an effective amount of a sclerosing foam whose
gaseous component consists of between 0.0001 % and 0.8% by volume
gaseous nitrogen, the balance being other gas, preferably physiologically
acceptable gas. The other possible ranges recited above for the percentage
of nitrogen apply and the options for the other gases recited above apply.
[098] Preferably the method of treatment comprises the injection of
10ml to 50ml of foam in a single injection, preferably 15m1 to 50ml, more
preferably 20m1 to 50m1, still more preferably 30m1 to 50ml of foam.
[099] According to the invention a method of treatment of the human
greater saphenous vein comprises treating substantially the entire greater
saphenous vein of one leg with a single injection of foam as described above.
[0100] According to the invention a method of treatment of a blood
vessel of diameter 7mm or greater so as to cause damage to the endothelium
of the vessel comprises injecting foam as described above.
[01011 A further factor in the inventors' developing understanding of the
behaviour in blood of bubbles comprising soluble gases is the phenomenon of
nitrogen diffusing out of blood and adjacent tissues and into the bubbles due
to a difference in the partial pressure of nitrogen in the bubbles as compared
with that in the surrounding blood and tissues. This phenomenon will
generally only occur when the partial pressure of nitrogen in the bubble is
lower than that in the surrounding blood and tissues.
[0102] It appears that carbon dioxide, and to a lesser extent oxygen,
will diffuse out of the bubble and go into solution in the surrounding blood
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relatively very quickly, so that the bubble will quite quickly reach a point
where
the partial pressure of nitrogen in the bubble will be higher than that in the
surrounding blood and tissues and, ultimately, the bubble will become
substantially pure nitrogen. As soon as the nitrogen partial pressure gradient
is reversed, nitrogen will come out of the bubble and into solution in the
blood,
though this will happen relatively slowly because of the low solubility of
nitrogen. This phenomenon will also be influenced by increasing saturation of
the surrounding blood with nitrogen, if this occurs to a significant extent.
This
phenomenon potentially affects the partial pressure gradient of nitrogen in
the
blood and may also mean that a limit for dissolution of nitrogen is reached if
the surrounding blood becomes fully saturated with nitrogen.
[0103] It is not at present understood to what extent localised
saturation of blood with nitrogen is a factor in the dissolution of the
bubbles in
a dispersing foam. Since the bloodstream in constant motion, however, it is
assumed that this effect will only ever be transient and will not unduly
affect
the overall picture of nitrogen dissolution.
[0104] It appears that the initial phase of rapid dissolution of carbon
dioxide and/or oxygen is critical: the shorter this period, the smaller the
volume of nitrogen which is able to diffuse into the bubble.
[0105] There are several possibilities for eliminating residual bubbles or
reducing them in size and/or number (apart from reducing the initial quantity
of nitrogen in the gas phase of the foam). One of these is to make the
bubbles as small as is practical. The smaller the bubble, the faster the
carbon dioxide and/or oxygen will dissolve out of the bubble and therefore the
shorter the time available for nitrogen from the blood to diffuse into the
bubble
before the partial pressure gradient for nitrogen reverses in favour of
nitrogen
diffusing out of the bubble.
[0106] Another is that of the patient breathing oxygen or air enriched
with oxygen, which has the effect of increasing the oxygen partial pressure in
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the blood at the expense of the nitrogen partial pressure. This technique is
known in the fields of diving and space exploration, where it has been used to
reduce the risk of the "bends", i.e. the tendency on depressurisation for
nitrogen to come out of solution in body tissues (as opposed to the blood in
blood vessels which is what we are concerned with here). As far as the
inventors are aware, it has never previously been proposed to use this
technique in connection with injecting gases into the vascular system.
[0107] According to an aspect of the invention a sclerosant foam is
composed of bubbles of which, ignoring bubbles of 1 micron or less diameter,
95% or more are of 150micron diameter or less and 50% or more are of
100micron diameter or less. Preferably, 95% or more of the bubbles are of
100micron diameter or less and 50% or more of the bubbles are of 50micron
diameter or less. More preferably, 95% or more of the bubbles are of
75micron diameter or less and 50% or more of the bubbles are of 30micron
diameter or less. Still more preferably, 95% or more of the bubbles are of
60micron diameter or less and 70% or more of the bubbles are of 30micron
diameter or less. Examples are presented below showing how foams with
these sorts of bubble distributions have been made.
[0108] These very small bubble foams have only to date been obtained
by the inventors by having a relatively dense formulation of the order of 0.3
to
0.5 g/ml, with a relatively high ratio of liquid to gas. Such a wet foam is
still
considerably less dense than blood and therefore will be buoyant when in a
vein full of blood. It is speculated that this buoyant characteristic may to
some extent be responsible for the advantageous behaviour of foam in the
vascular system in terms of displacing blood. However, the dense foams
produced to date by the inventors behave essentially as a liquid in terms of
their rheological properties - they are not "stiff'.
[0109] It is not impossible that these dense but somewhat fluid foams
may have a sufficiently good therapeutic effect to be useful and may also
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eliminate or reduce the residual gas problem. However, it is probable that the
rheological properties of the foam in blood are important, and that a "stiff'
foam is desirable effectively to displace blood and thus allow consistent,
uniform application of the active to the interior of the vessel wall. For this
reason it may be desirable to add a further ingredient to the foam in order to
increase its stiffness/viscosity, either by adding a viscosity-enhancing
additive
to the formulation or by adding an agent which increases the foaming
capacity of the formulation.
[0110] Such ingredients could be, without limitation, Polysorbate 20,
Polysorbate 80 or Polygeline . Alternatively, glycerol and PVP may be added.
[0111 ] A foam with a bubble size distribution falling within the
definitions set out above may be created by passing gas and liquid repeatedly
through a fine mesh, e.g. a 5 micron mesh. Repeated passages through the
mesh reduce the bubble size, though there appears to be a limit on this.
[0112] It is envisaged that other known techniques for agitating a gas
and liquid mixture at high energy could be applied to make even finer
bubbles. For example sonic or ultrasonic agitation of a mixing stream of gas
and liquid could be used, or alternatively a mixture of beating the gas and
liquid by mechanical means, supplemented by the application of sonic or
ultrasonic energy.
[0113] The inventors have also prepared a foam having an average
bubble size in the range 50micron to 80micron by adapting a canister to alter
the ratio of liquid and gas being passed through a mesh.
[0114] A further aspect of the invention is a pressurised canister
product adapted to dispense a sterile gas and sclerosing liquid mixture in
predetermined proportions into a syringe, as a solution to some of the issues
with extemporaneous preparation of foam. Thus a pressurised canister is
provided - which may be of any suitable material such as anodised
aluminium or even glass - containing sterile gas and sclerosing liquid and
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arranged to dispense the correct volume of liquid and gas into a syringe. It
is
envisaged that the canister would contain sterile gas with a very low nitrogen
concentration etc. as defined above. The canister may have a pierceable
septum for puncturing with a hypodermic needle, or it may have a break seal
which is arranged to be broken by insertion of a syringe luer nozzle.
[0115] In the latter case, a syringe luer nozzle could be inserted into
the canister in a sealing fashion, with the syringe nozzle pointing upwards.
Liquid in the canister would be dispensed first under pressure, followed by
equalisation of the pressure in the canister and syringe. The pressure and
volume of gas in the canister could of course be arranged so that the correct
proportions of gas and liquid are dispensed. Alternatively, the canister could
be provided with an internal dip tube so that the same effect is achieved with
the canister in an upright orientation.
[0116] Also according to the invention is provided a method of
preparing a sclerosing foam which includes the step of cooling the ingredients
of the foam to a sub-ambient temperature prior to generation of the foam. A
suitable temperature range might be 0 to 15 degrees Celsius, preferably 0 to
10 degrees, more preferably 3 to 7 degrees. Decreasing temperature
increases liquid viscosity and, in this way, the inventors believe the half
life of
the foam could be extended. Since, during decay of a foam, the bubble size
tends to increase, this methodology may help reduce the average size of
bubbles over time in the body and thereby reduce residual bubbles.
[0117] Also according to the invention, and in line with the reasoning
presented earlier, a method of angiologic treatment of a patient comprises
causing the patient to breathe oxygen gas or oxygen-enriched air for a
predefined period prior to injection of foam as described above. Preferably
the predefined period is 1 to 60 minutes, more preferably 1-20 minutes, more
preferably 5-10 minutes.
[0118] Another embodiment of the present invention provides a foam,
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that, for example, can be used in the elimination of blood vessels and
vascular malformations, that are made available by the method and devices
of the invention, comprising a physiologically acceptable gas that is readily
dispersible in blood together with an aqueous sclerosant liquid wherein in
that
the foam has a density of from 0.07 to 0.19 g/cm.
[0119] In one embodiment, the foam is capable of being passed down
a 21 gauge needle without reverting back to gas and liquid by more than
10%, based on liquid content reverting back to unfoamed liquid phase.
[0120] Half-life is conveniently measured by filling vessel with a known
volume and weight of foam and allowing liquid from this to drain into a
graduated vessel, the amount drained in a given time allowing calculation of
half-life i.e. of conversion of microfoam back into its component liquid and
gas
phases. This is preferably carried out at standard temperature and pressure,
but in practice ambient clinic or laboratory conditions will suffice.
[0121 ] Most conveniently the funnel is pre-equilibrated in a water bath
to ensure a temperature of 25 C before drying and application of foam.
Placing of a foam filled syringe upside down, without its plunger, above the
funnel leading into a graduated receptacle allows convenient measurement of
this parameter.
[0122] In one embodiment, the foam, on passage through said needle,
does not revert back to unfoamed liquid by more than 5% based on liquid
content, still more preferably by no more than 2%. This is measured by
measuring the change in volume of the foam versus the liquid.
[0123] In one embodiment, the foam is capable of being passed down
a needle while retaining at least 50% by number of its gas bubbles of at least
25 m diameter at no more than 200 m diameter. This is conveniently
measured under ambient conditions, more preferably at STP.
[0124] In one embodiment, the gas includes less than 40% v/v
nitrogen. Preferably the density of the foam is from 0.09 to 0.16 g/mL, more
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preferably 0.11 g/mL to 0.14 g/mL.
[0125] In one embodiment, the foam density, which is a measure of
liquid/gas ratio, is from 0.13 to 0.14 g/cm and the half-life is at least 2.5
minutes. The foam more preferably does not move outside of its parameters
of bubble size set out above in such time.
[0126] In one embodiment, the gas consists of at least 50% oxygen or
carbon dioxide, more preferably 75% or more oxygen or carbon dioxide and
most preferably at least 99% oxygen or carbon dioxide, e.g. substantially
100% oxygen or carbon dioxide. Preferably the oxygen or carbon dioxide is
medical grade.
[0127] As discussed above, addition of glycerol to the aforesaid
sclerosant imparts a longer half-life to the resultant foam. However, glycerol
may increase density and also produces a tendency for the meshes to block
up when using a mesh device as described above, so should be used
carefully where the device it is produced from may be used multiple times or
the bag-on-valve concept is used.
[0128] The invention also provides:
[0129] a method of treating a patient in need of sclerotherapy of a
blood vessel comprising administering a foam as described above to that
blood vessel; use of a foam described above for the manufacture of a
medicament for sclerotherapy; and a foam as described above for use in
therapy.
[0130] Accordingly the one aspect of the present invention provides a
method for producing a foam suitable for use in scleropathy of blood vessels,
particularly veins, characterized in that it comprises passing a mixture of a
physiologically acceptable blood dispersible gas and an aqueous sclerosant
liquid through one or more passages having at least one cross-sectional
dimension of from 0.1 to 15 m, the ratio of gas to liquid being controlled
such
that a foam is produced having a density of between 0.07 g/mL to 0.19 g/mL
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and a half-life of at least 100 seconds.
[0131] Apparatuses for generating foam
[0132] There are a number of issues with the current practice of
extemporaneous preparation of foam, the use of air as the gas being only one
of these. Other issues are the consistency of the product, which is by nature
highly variable because it depends on the physician selecting the gas to
liquid
ratio and then pumping the gas and air mixture a given number of times
and/or at a given speed to obtain the right product. Foams are highly variable
and different bubble sizes and densities will have different safety and
efficacy
profiles.
[0133] Very recently, a machine has been made available which is
designed to receive two syringes and apply a given number of pumps at a
given rate to achieve a roughly consistent product. The machine is called
"Turbofoam" but the inventors are not at present aware who is marketing the
machine. Two syringes are loaded into it (one of which is loaded with
sclerosant solution). When activated, the machine automatically draws a
predetermined quantity of atmospheric gas into the syringes and cycles the
syringes until a foam of the desired properties is made.
[0134] Clearly, the arrangement described above addresses at least
the issues of reproducibility of the foam as regards the gas/liquid ratio
(provided the correct amount of liquid is loaded initially by the user) and
also
the number and speed of cycles. However, it is obviously also quite
inconvenient in many respects and sterility may also be compromised by build
up of bacteria in the gas channels of the machine, for example.
[0135] The solution proposed by the inventors is to provide a sterile
pack containing one or two syringes, optionally together with any connectors
etc. The syringe or syringes is/are pre-loaded with the correct volumes of gas
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and sclerosing liquid. Most syringes are made from plastics material such as
polypropylene which allows gas to permeate through it over time. Therefore,
the packaging is preferably substantially gas-impermeable and the
atmosphere in the pack is preferably substantially the same composition as
the gas pre-loaded into the syringe. This sort of packaging is well known in
itself and examples include metallised plastic sheeting e.g. an aluminium and
polyethylene laminate.
[0136] According to one aspect of the invention, there is provided a
substantially sterile pack comprising:
[0137] a syringe charged with a liquid sclerosing agent and a gas
mixture comprising physiologically acceptable gas, such as, for example,
between 0.0001 % and 0.8% gaseous nitrogen with the balance being other
gas, such physiologically acceptable gas; and
[0138] a gas atmosphere inside the pack having substantially the same
composition as the said gas mixture in the syringe.
[0139] In one embodiment, the gas mixture consists of 0.001 % to 0.8%
gaseous nitrogen, preferably 0.01 % to 0.8%, more preferably 0.01 % to 0.7%,
still more preferably 0.01 % to 0.6%.
[0140] In one embodiment, the said other gas is oxygen, carbon
dioxide or a mixture thereof. Optionally, a small percentage (e.g. 0.1 to 5%)
of a tracer gas, which is not found in significant amounts in the atmosphere,
is
added to allow leaks to be detected. Such a gas might be e.g. helium, neon,
argon, xenon or any other gas which is found in trace concentrations (0.01 %)
in atmospheric air.
[0141 ] To avoid contamination, the pack contents may be at slightly
above atmospheric pressure. This may be achieved by manufacturing the
pack at an ambient temperature below standard room temperature. Once the
pack enters normal ambient surroundings, the temperature increase of the
atmosphere inside the pack will ensure a slight overpressure.
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[0142] Manufacture of the packaged product would be carried out in
aseptic conditions, using techniques standard in that field.
[0143] This pre-packaged product may include one syringe of the type
comprising a barrel, a first plunger and a second plunger, the second plunger
having an apertured plunger head which is adapted to be movable within the
barrel independently of the first plunger.
[0144] Alternatively the syringe may be a conventional one, containing
an appropriate amount of gas as described above. A further syringe
containing sclerosing agent could be provided in the same or a different pack,
together with the connectors, three way valves, etc necessary to perform any
of the known techniques for extemporaneous foam preparation.
[0145] In use, the pack is opened and the usual technique followed for
generating foam, without the need to measure out liquid or gas. In the case
of a two syringe technique, the syringes can be supplied ready connected, to
increase convenience and remove a potential source of contamination.
[0146] Optionally, the pack may include a syringe connector which
incorporates a fine mesh with apertures of 1-200micron, preferably 2 to 50,
more preferably 3 to 20 micron maximum dimensions. Alternatively, if a
single syringe device is used, the apertures in the plunger may be provided
by a mesh with pores of these proportions.
[0147] Optionally, the package could constitute a cartridge for a foam
generating machine similar to the "Turbofoam" described above.
[0148] A further solution to the issues with extemporaneous foam
preparation has been proposed by the inventors. This is to provide a
pressurised canister - which may be of any suitable material such as
anodised aluminium or even glass - containing sterile gas and sclerosing
liquid and arranged to dispense the correct volume of liquid and gas into a
syringe. It is envisaged that the canister would contain sterile gas as
defined
above. The canister may have a pierceable septum for puncturing with a
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hypodermic needle, or it may have a break seal which is arranged to be
broken by a syringe luer nozzle.
[0149] In the latter case, a syringe luer nozzle could be inserted into
the canister in a sealing fashion, with the syringe nozzle pointing upwards.
Liquid in the canister would be dispensed first under pressure, followed by
equalisation of the pressure in the canister and syringe. The pressure and
volume of gas in the canister could of course be arranged so that the correct
proportions of gas and liquid are dispensed. Alternatively, the canister could
be provided with an internal dip tube so that the same effect is achieved with
the canister in an upright orientation.
[0150] It is found that passing a stream of the sclerosant liquid and the
gas under pressure through one or more passages of 0.1 .im to 15 m as
described provides a stable blood dispersible gas based sclerosant injectable
foam that was previously thought to be only producible by supply of high
amounts of energy using high speed brushes and blenders.
[0151] The aerosol, dispersion or macrofoam is preferably produced by
mixing the gas and liquid from respective flows under pressure. The mixing
conveniently is carried out in a gas liquid interface element such as may be
found in aerosol canisters. The interface device may however be very simple,
such as a single chamber or passage of millimetre dimensions, i.e. from 0.5
to 20 mm diameter, preferably 1 to 15 mm diameter, into which separate
inlets allow entry of gas and liquid. Conveniently the interface is of design
which is commonly found in aerosol canisters but which is selected to allow
the correct ratio of gas to liquid to allow formation of a foam of the
presently
defined density. Suitable inserts are available from Precision Valves
(Peterborough UK) under the name Ecosol and are selected to produce the
ratio specified by the method above.
[0152] However, the mixing of gas and liquid may also be brought
about within a dip-tube leading from the sclerosant solution located in the
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bottom of a pressurized container where holes in the dip-tube allow gas to
enter into a liquid stream entering from the bottom of the tube. In this case
the
holes may be of similar diameter to the Ecosol holes. Such holes may be
conveniently produced by laser drilling of the dip-tube.
[0153] The one or more passages through which the aerosol or
macrofoam so produced are passed to produce the stable foam preferably
have diameter of from 4 m to 22 m, more preferably from 5 m to 11 m
where simple passages are provided, such as provided by openings in a
mesh or screen, e.g. of metal or plastics, placed perpendicular to the flow of
gas/liquid mixture. The passage is conveniently of circular or elliptical
cross
section, but is not necessarily so limited. A number of such meshes or
screens may be employed along the direction of flow.
[0154] Most preferably the passages are provided as multiple openings
in one or more elements placed across the flow. Preferably the elements are
from 2 to 30 mm diameter, more preferably 6 to 15 mm diameter, face on to
the flow, with 5 to 65% open area, e.g. 2% to 20% open area for woven
meshes and 20% to 70% open area for microporous membranes. Openings
in a porous material, such as provided in a perforated body, preferably
provide several hundreds or more of such passages, more preferably tens or
hundred of thousands of such passages, e.g. 10,000 to 500,000, presented to
the gas liquid mixture as it flows. Such material may be a perforated sheet or
membrane, a mesh, screen or sinter. Still more preferably a number of sets of
porous material are provided arranged sequentially such that the gas and
liquid pass through the passages of each set. This leads to production of a
more uniform foam.
[0155] Where several elements are used in series these are preferably
spaced 1 to 5 mm apart, more preferably 2 to 4 mm apart e.g. 3 to 3.5 mm
apart. For some embodiments of the present invention it is found that the
passage may take the form of a gap between fibres in a fibrous sheet placed
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across the path of the gas/liquid flow, and the dimension described in not
necessarily the largest diameter, but is the width of the gap through which
the
gas/liquid aerosol or macrofoam must flow.
[0156] Alternatively the method provides for passing the mixture of gas
and liquid through the same set of passages, e.g. as provided by one or more
such porous bodies, a number of times, e.g. from 2 to 2,000, more preferably
4 to 200 times, or as many times as conveniently results in a foam of the
required bubble size distribution set out above. It will be realized that the
more times the foam passes through the meshes, the more uniform it
becomes. Where multiple passes through the meshes are possible, a large
mesh size may be desirable, e.g, 20 to 300 m, such as 40 to 200 m, such
as 60 to 150 m.
[0157] The pressure of the gas used as it is passed through the
passages will depend upon the nature of the mechanism used to produce the
foam. Where the gas is contained in a pressurized chamber and passes only
once through the mesh, such as in an aerosol canister, in contact with the
liquid, suitable pressures are typically in the range 0.01 to 9 bar over
atmosphere. For use of meshes, e.g. 1 to 8 meshes arranged in series,
having apertures of 10-20 m diameter, 0.1 to 5 atmospheres over bar will,
inter alia, be suitable. For use of 3-5 meshes of 20 m aperture it is found
that 1.5-1.7 bar over atmospheric is sufficient to produce a good foam. For a
0.1 m pore size membrane, a pressure of 5 bar or more over atmospheric
pressure is preferred.
[0158] In one preferred form of the invention the passages are in the
form of a membrane, e.g. of polymer such as polytetrafluoroethylene, wherein
the membrane is formed of randomly connected fibres and has a rated
effective pore size which may be many times smaller than its apparent pore
size. A particularly suitable form of this is a biaxially oriented PTFE film
provided by TetratecTM USA under the trademark TetratexTM, standard ratings
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being 0.1 to 10 m porosity. Preferred pore sizes for the present method and
devices are 3 to 7 m. This material may be laminated with a porous backing
material to give it strength and has the advantage that one pass through may
be sufficient to produce a foam that meets the use requirements set out
above with regard to stability. However, it will evident to those skilled in
the art
that use of more than one such membrane in series will give a still more
uniform foam for given set of conditions.
[0159] It is believed that the combination of provision of a stream of
solution and gas under pressure through an aerosol valve and then flow
through the passages, e.g. pores in a mesh, screen, membrane or sinter
provides energy sufficient to produce a stable aqueous liquid soluble gas,
e.g.
carbon dioxide and/or oxygen, based sclerosant foam that was previously
thought to be only producible by supply of high amounts of energy using high
speed brushes and blenders as described in the prior art.
[0160] A most preferred method of the invention provides a housing in
which is situated a pressurisable chamber. For sterile supply purposes this
will at least partly filled with a sterile and pyrogen free solution of the
sclerosing agent in a physiologically acceptable aqueous solvent but
otherwise may be charged with such at the point of use. This convenient
method provides a pathway by which the solution may pass from the
pressurisable chamber to exterior of the housing through an outlet and more
preferably a mechanism by which the pathway from the chamber to the
exterior can be opened or closed such that, when the container is
pressurized, fluid will be forced along the pathway and through one or more
outlet orifices.
[0161] The method is particularly characterized in that the housing
incorporates one or more of (a) a pressurized source of the physiologically
acceptable gas that is readily dispersible in blood, and (b) an inlet for the
admission of a source of said gas; the gas being contacted with the solution
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on activation of the mechanism.
[0162] The gas and solution are caused to pass along the pathway to
the exterior of the housing through the one or more, preferably multiple,
passages of defined dimension above, through which the solution and gas
must pass to reach the exterior, whereby on contact with, e.g. flow through,
the passages the solution and gas form a foam.
[0163] Preferably the gas and liquid pass through a gas liquid interface
mechanism, typically being a junction between a passage and one or more
adjoining passages, and are converted to an aerosol, dispersion of bubbles or
macrofoam before passing through the passages, but as explained they may
be converted first to a macrofoam, e.g. by shaking of the device, e.g., by
hand, or mechanical shaking device.
[0164] In another aspect of the present invention there is provided a
device for producing a foam suitable for use in scleropathy of blood vessels,
particularly veins, comprising a housing in which is situated a pressurisable
chamber containing a solution of the sclerosing agent in a physiologically
acceptable solvent referred to in the first aspect; a pathway with one or more
outlet orifices by which the solution may pass from the pressurisable chamber
to exterior of the device through said one or more outlet orifices and a
mechanism by which the pathway from the chamber to the exterior can be
opened or closed such that, when the container is pressurized and the
pathway is open, fluid will be forced along the pathway and through the one
or more outlet orifices
[0165] said housing incorporating one or more of (a) a pressurized
source of physiologically acceptable gas that is dispersible in blood and (b)
an
inlet for the admission of said gas; the gas being in contacted with the
solution on activation of the mechanism such as to produce a gas solution
mixture
[0166] said pathway to the exterior of the housing including one or
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more elements defining one or more passages of cross sectional dimension,
preferably diameter, 0.1 m to 15 m, through which the solution and gas
mixture is passed to reach the exterior of the device, said passing of said
mixture through the passages forming a foam of from 0.07 to 0.19 g/mL
density and of half-life at least 2 minutes.
[0167] Preferably the apparatus includes a chamber, e.g. such as in a
sealed canister, charged with the blood dispersible gas and the sclerosant
liquid, e.g. in a single chamber, the device pathway including a dip tube with
an inlet opening under the level of the liquid in this chamber when the device
is positioned upright. Preferably the dip-tube has an outlet opening at a gas
liquid interface junction where the gas, which resides in the chamber above
the liquid, has access to the pathway to the device outlet. The pathway is
opened or closed by a valve element which is depressed or tilted to open up a
pathway to the exterior of the device, whereby the liquid rises up the dip
tube
under gas pressure and is mixed in the interface junction with that gas to
produce an aerosol, dispersion of bubbles in liquid or macrofoam.
[0168] Either inside the pressurisable chamber disposed in the
pathway to the valve, or on the downstream side of the valve, is provided an
element having the one or more passages described in the first aspect
mounted such that the gas liquid mixture, i.e. dispersion of bubbles in
liquid,
aerosol or macrofoam,, passes through the passage or passages and is
caused to foam. This element may conveniently be located in a cap on the
canister in between the valve mounting and an outlet nozzle. Conveniently
depression of the cap operates the valve. Alternatively the element is within
the canister mounted above the gas liquid interface.
[0169] In an alternate embodiment of this device the gas liquid
interface may comprise holes in the dip tube above the level of the liquid in
the canister inner chamber.
[0170] The gas pressure employed will be dependent upon materials
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being used and their configuration, but conveniently will be 0.01 to 9 bar
over
atmospheric, more preferably 0.1-3 bar over atmospheric, and still more
preferably 1.5-1.7 bar over atmospheric pressure.
[0171 ] A preferred device of this aspect of the invention is of the 'bag-
on-valve' type. Such device includes a flexible gas and liquid tight
container,
forming a second inner chamber within the pressurisable chamber, which is
sealed around the dip-tube and filled with the liquid. More preferably the dip-
tube has a one-way valve located at a position between its end located in the
sclerosant liquid and the gas liquid interface junction, which when the
passage to the exterior is closed, remains closed such as to separate the
liquid from the physiologically acceptable blood dispersible gas around it in
the chamber. On opening the pathway to the exterior, the one way valve also
opens and releases liquid up the dip-tube to the gas liquid interface where an
aerosol is produced which is in turn then passed through the passages to be
converted to foam. A suitable one-way valve is a duck-bill type valve, e.g.
such as available from Vernay Labs Inc, Yellow Springs, Ohio, USA. Suitable
bag-on-valve can constructions are available from Coster Aerosols,
Stevenage, UK and comprise an aluminium foil/plastics laminate.
[0172] Conveniently the one way valve is located at the top of the dip-
tube between that and the gas liquid interface junction, i.e. an Ecosol
device.
This allows filling of the bag before application of the one way valve,
followed
by sterilization of the contents, whether in the canister or otherwise.
[0173] Such a preferred device has several potential advantages.
Where oxygen is the gas, this is kept separate from the liquid before use and
thus reduces possibility of oxygen radicals reacting with organic components
in the liquid, e.g. during sterilization processes such as irradiation. Where
carbon dioxide is the gas, storage can lead to high volumes of gas dissolving
in the liquid, which on release to the atmosphere or lower pressure, could out-
gas and start to destroy the foam too quickly. Such separation also prevents
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the deposition of solidified sclerosing agent components in the dimension
sensitive orifices of the device in an unused can in storage or transit,
particularly should that be oriented other than upright.
[0174] It is preferred that the gas liquid interface is provided as a
defined orifice size device such as the Ecosol device provided by Precision
Valve Peterborough UK. For a device where the passages of defined
dimension are outside of the pressurized chamber, i.e. mounted on the valve
stem, the ratio of area of the gas holes to the liquid holes should be of the
order of 3 to 5, preferably about 4. Where the passages are inside the
pressurized chamber this is preferably higher.
[0175] Another aspect of the invention provides a device for producing
a foam suitable for use in sclerotherapy of blood vessels, particularly veins,
comprising a housing in which is situated a pressurisable chamber, at least
part filled or fillable with a solution of a sclerosing agent in a
physiologically
acceptable solvent and/or a physiologically acceptable blood dispersible gas;
a pathway by which the contents of the chamber may be passed to exterior of
the housing through one or more outlet orifices and a mechanism by which
the chamber can be pressurized such that its contents pass to the exterior
along the pathway and through one or more outlet orifices
[0176] said pathway to the exterior of the housing or the
chamber including one or more elements defining one or more passages of
cross sectional dimension, preferably diameter, 0.1 m to 15 m through
which the contents of the chamber may be passed, whereby on passing
through the passages the solution and gas form a foam of from 0.07 to
0.19 g/mL density and having a half-life of at least 2 minutes.
[0177] The elements defining the passages in the pathway or chamber
may be static or may be moveable by manipulation of the device from outside
of its interior chamber.
[0178] Preferably the housing is a container defining a chamber in
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which is situated the solution and gas under pressure and the pathway is a
conduit leading from the chamber in the interior of the container to a valve
closing an opening in the container wall.
[0179] Preferred forms of the one or more elements defining the
multiple passages for use in the device of the present invention are meshes,
screens or sinters. Thus one or more meshes or perforated screens or sinters
will be provided, with some preferred forms employing a series of such
elements arranged in parallel with their major surfaces perpendicular to the
path of solution/gas expulsion.
[0180] It is preferred that all elements of any of the devices according
to the invention having a critical dimension are made of a material that does
not change dimension when exposed to aqueous material. Thus elements
with such function such as the air liquid interface and the element defining
the
passages of 0.1 m-15 m dimension preferably should not be of a water
swellable material such as Nylon 66 where they are likely to be exposed to
the solution for more than a few minutes. Where such exposure is likely these
parts are more preferably being fashioned from a polyolefin such as
polypropylene or polyethylene.
[0181] Preferably the canister is sized such that it contains sufficient
gas and solution to form up to 500 mL of foam, more preferably from 1 mL up
to 200 mL and most preferably from 10 to 60 mL of foam. Particularly the
amount of gas under pressure in such canisters should be sufficient to
produce enough foam to treat, i.e. fill, at least one varicosed human
saphenous vein. Thus preferred canisters of the invention may be smaller
than those currently used for supply of domestic used mousse type foams.
The most preferred canister device is disposable after use, or cannot be
reused once opened such as to avoid problems of maintaining sterility.
[0182] It may be preferred to incorporate a device which maintains gas
pressure in the canister as foam is expelled. Suitable devices are such as
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described under trademarked devices PECAP and Atmosol. However, where
a significant headspace or pressure of gas is provided this will not be
necessary.
[0183] The canister system has some drawbacks, however. It is
relatively complex and thus expensive. Furthermore, the initial quantity of
foam generated using a canister system can be of unpredictable quality and
thus tends to be diverted off to waste prior dispensing foam for use. It is
not
easy to deliver foam direct from a pressurized canister into a cannula in a
patient's vein; although this is theoretically possible, it would require
special
valve/control arrangements on the canister output to allow for the delivery
rate
to be highly controllable by the clinician administering the treatment. A
further
issue is that, whenever dispensing of foam is stopped or slowed significantly,
it is necessary on re-starting to divert a quantity of foam to waste again
before
dispensing usable foam.
[0184] For all these reasons, the canister product mentioned above,
though a well designed and highly effective system, is designed to deliver
foam product into a syringe for subsequent administration to a patient. A
special foam transfer unit is used for this purpose. The syringe nozzle is
inserted into a port on this transfer device and the device is then used to
divert the first portion of foam before charging the syringe with usable foam.
[0185] A further issue is that the foam, once made, immediately starts
to change - liquid drains out and bubbles coalesce. A period of time is
required time for the clinician to divert an initial quantity of foam from a
canister, charge a syringe with good foam, connect it to a line to a patient's
vein and administer the foam. This time will vary with different clinicians
and
even the same clinician will not always take the same length of time.
Furthermore, each treatment is different and the foam will be injected over a
different period; sometimes the clinician will stop dispensing foam for a
short
period and then recommence. All this time, the properties of the foam will be
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changing.
[0186] There are other techniques for generating foam for use in
sclerotherapy, including the so called "Tessari" and "DSS" techniques, each
of which involves pumping liquid sclerosant and gas between two syringes.
These two techniques are widely used for generating sclerosing foams made
with air, and there are also a number of other less widely used techniques.
Although these techniques are simpler than a canister system, they offer no
solutions to the problems mentioned above and they also have their own
problems such as unpredictability of the product and the difficulty in using
any
gas other than ambient air.
[0187] The inventors realized that it would be desirable to have a
device which could be connected directly to the patient and would generate
foam as it was needed, so that the foam had the minimum possible time to
degrade before entering a patient's vein. Ideally the device would also not
have the problem of producing an initial quantity of poor foam. The device
should be suitable for containing a gas other than air for incorporation into
the
foam.
[0188] The inventors also realized that, particularly for a highly soluble
gas, the device should ideally not store the gas together with the liquid
under
a pressure substantially greater than atmospheric. With a soluble gas,
especially a highly soluble gas such as carbon dioxide, storing the gas and
liquid under pressure can contribute to the speed of decay of the foam. This
is because the pressurised gas tends to go into solution in the sclerosant
liquid. On exit of the foam, the gas comes out of solution into the bubbles
thereby accelerating degradation of the foam. Pressurising the gas also, of
course, adds to the complexity and expense of the system.
[0189] According to a first aspect of the invention, a device for
generating and dispensing foam for therapeutic use comprises:
(a) a housing;
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(b) the housing having a first chamber of adjustable volume containing
gas at substantially atmospheric pressure;
(c) the housing further having a second chamber of adjustable volume
containing sclerosant solution;
(d) an outlet for dispensing the liquid and sclerosant solution in the
form of a foam and a flow path communicating between the outlet
and the said first and second chambers;
(e) the flow path including a region in which mixing of the gas and
solution takes place;
(f) a foaming unit located downstream of the mixing region, the
foaming unit having holes with a dimension transverse to the flow
direction of between 0.1 and 100 micron.
[0190] It is preferred that the hole dimension be from 1 to 50micron,
more preferably 2 to 20micron, still more preferably 3 to 10micron. These
holes may be provided by a mesh, perforated screen, sinter or fabric, for
example. Although the shape and orientation of the holes may not be regular,
the unit should have a major proportion (greater than 50%, preferably greater
than 80%) of holes where at least one dimension in a direction approximately
transverse to the flow should be in the ranges specified above.
[0191] In use, the volumes of the first and second chamber are
adjusted in order to drive the gas and solution out of the chambers and
through the mixing region and foaming unit. A mixture of gas and solution is
formed as the gas and liquid pass through the mixing region and then a foam
is formed as the mixture passes through the foaming unit.
[0192] It is preferable for the liquid and gas to be driven through the
mixing region and foaming unit at a flow rate which falls within a
predetermined range, the desired flow rate range depending on the
characteristics of the liquid and of the gas, the characteristics of the
mixing
region and foaming unit, and possibly other characteristics of the system.
The volume of the chambers may be varied manually to create the foam, but
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it is preferred that the adjustment of the chambers be carried out using some
other source of motive power, e.g. an electric, clockwork, pneumatic or
hydraulic motor or by the direct action of pressurized gas or even a simple
spring. An on/off control is preferably provided for the user to commence and
to stop delivery of foam.
[0193] The source of motive power may be provided as part of the
device. Alternatively, the device may be designed as a cartridge for insertion
into a delivery device which may for example be similar to known devices for
automatically delivering medication from a syringe over an extended period of
time.
[0194] The device may be configured with a flexible housing in form of
e.g. a bag with dual chambers, or two separate bags, connected to a mixing
region and foaming unit. The bag or bags may then be rolled up in a delivery
device or the contents squeezed out by some other mechanical means.
Desirably, the chambers are of a size and shape which allow them to be
squeezed out at the same rate, in terms of velocity, to achieve a desired foam
density. This allows the mechanical means for squeezing the chambers to be
of a more simple design.
[0195] Alternatively the device may be configured as a syringe, with the
first and second chambers having respective plungers which may be
depressed in order to expel the contents. Preferably size and shape of the
chambers, most notably their cross sectional areas, are selected so that the
plungers may be driven at the same speed to achieve a desired ratio of gas to
liquid in the foam.
[0196] As discussed above, the device may be suitable for connection
to a cannula needle, optionally via a line, for delivery of foam into the
body,
e.g. into a vessel such as a blood vessel, especially a varicose vein or other
venous malformation. Since the foam is generated by the same action which
expels the foam from the outlet, it may be possible to connect the cannula to
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the outlet of the device and administer foam to a patient at the same time as
generating it. This is clearly a much simpler procedure than generating the
foam, drawing it up into a syringe, connecting the syringe to a line/cannula
and then administering the foam.
[0197] According to the invention, a method for administering a foam to
the human body, e.g. into a vessel such as a blood vessel, especially a
varicose vein or other venous malformation, comprises the steps of: (a)
schlerosant foam generating device to a cannula needle inserted into a
patient; and (b) operating the device to generate and dispense foam to the
patient. Specifically, the steps may include:
(a) connecting a device as described above to a cannula needle
inserted into a patient;
(b) adjusting the volume of the said first and second chambers so as to
generate and deliver foam to the patient.
[0198] A further advantage of the generation and delivery of the foam
in a single step is that the foam has very little time to degrade prior to
entering
the body to perform its function, e.g. the sclerosis of a varicose vein. The
device is therefore particularly suitable for generating foams with very
soluble
gases, such as carbon dioxide or nitrous oxide, which tend to revert to their
gaseous and liquid phases relatively quickly.
[0199] Since the gas and liquid are stored in separate chambers until
formation of the foam, there is very little possibility for the gas to become
dissolved in the liquid, which tends to happen with the pressurized canister
systems described in the prior art.
[0200] According to the invention, a foam is provided which is made
with a sclerosant solution, e.g. polidocanol solution, and a gas, wherein, on
creation of the foam, the dissolved level of the gas in the solution is not
substantially higher than that of the solution when exposed to atmosphere at
s.t.p., and wherein the gas is at least 70% by volume carbon dioxide, more
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preferably: at least 900/6 carbon dioxide, still more preferably substantially
100% carbon dioxide. The gas may also include 0.1 to 50% oxygen:
Alternatively the gas may be substantially 100% nitrous oxide or a mixture of
nitrous oxide and carbon dioxide.
5- [0201']Also according to, the Invention, .a. device is provided for
generating foam from. a scierosant.liqui i, e:g. poiidocanol solution, and a
soluble gas as described above, wherein the device, Incorporates a chamber
in which the gas is stored at substantially atmospheric.: pressure,
Preferably,
the device further comprises a chamber in which sclerosant liquid is stored.
Preferably, the device further includes a foaming unit:for creating a foam
from
the gas and sclerosant::,liquid, the foaming unit having holes with a
dimension
transverse. to the flow direction of between 0;1 and 100 micron, such as 1 to
50, 2 to 20, 3 to 1A. and especially about 5.
[0202] Further features and,:advantages of the Invention will be
apparent from the following description of:varlous specific embodiments,
which is made with reference to the accompanying drawings.
[0203] One embodiment of a device according to the invention comprises a
syringe type device comprising a syringe barrel having an annular chamber
containing gas and a central chamber for receiving a cartridge of sclerosant
solution,
e.g. 1% polidocanol solution. Figure 1 shows a syringe barrel 1.1 in a storage
condition with its open ends closed with seals 1.2 of metal/plastic laminate
material.
The barrel 1.1 comprises an outer cylindrical wall 1.3 having a conical
tapered end
portion 1.4 at the front, from which extends a standard luer nozzle 1.5.
Disposed
within the outer cylindrical wall is an inner cylindrical wall 1.6 defining an
inner
chamber 1.14. The front of the inner wall 1.6 is partly closed by and end face
1.8,
in which is formed an orifice 1.9 with a frangible seal 1.10. The inner wall
is
supported at the front end by a web 1.11, in which apertures 1.12 are formed.
[0204] The outer and inner walls 1.3, 1.6 define between them an annular
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space 1.7 which is filled with substantially 100% pure carbon dioxide gas. The
annular space 1.7 communicates with the interior space of the luer nozzle 1.5
via the
apertures 1.12 in the web 1.11. Located at the rear of the barrel, in the
annular
space 1.7, is an annular plunger seal 1.13 of.resilient plastics material
which seals
against the outer and inner cylindrical walls 1.3, 1.6.
10205] Figure:.2 shows a cartridge comprising a glass tube 20: filled with
I % poiidocanol and sealed at each and by a resilient plastics bung. 21. One
or both of the bungs may function as a plunger seal; that is to say it may be
movable down the length of the tube whilst retaining a sealing:_contain with.
the Interior wall of the tuube The: cartridge of Figure 2 is not, suitable for
use
with the syringe barrel described above, but could be used with a modified
version of the barrel. as discussed below.
10206] Figure 3 shows,a cartridge suitable for use with the syringe
barrel described above with reference to Figure 1. The cartridge comprises a:
glass- tube 30' which Is filled with 10/6 poildocano[ solution. At. the rear
end of
the tube 300 is a resilient bung 31 which is. capable of functioning as a
plunger
seal as described above: At the front end of the tube. is an end face 32 in
which is located a nozzle 33,. sealed with an end cap 34. The size and shape
of the tube. 30 complements the shape of the inner wall 6 of the. syringe
barrel
of Figure 1. In particular; the diameter of the tube 30 is such that the tube
is a
close fit In the interior space 14 defined within the1nner wall 6 of the
barrel 1,
and the nozzle 33 of the: cartridge is sized so that, when fully inserted Into
the
interior chamber 14 of the barrel,. It protrudes through the orifice S: In the
front
of the chamber 1.4 (the.:end cap; 34 having first been removed)..
(207] Cartridges of the. type shown in. Figures 2 and 3 are well known
for liquid drugs.. The cartridges are fitted to specially designed :injection
devices to administer the drug, and. the empty cartridge: then removed from
the device and disposed of..
[0208] Figure 4 shows a cartridge 30. as shown in Figure 3 being:
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inserted into the barrel of Figure 1. Note that the end cap 34 of the
cartridge
has been removed.
[0209] Figure 5 shows the cartridge 30 fully inserted into the barrel 1
such that the nozzle 32 seals in the orifice 9 of the interior chamber 14 of
the
barrel. A syringe plunger stem 40 is fitted to the rear of the syringe barrel
1.
The plunger stem 40 comprises a disc 43 for applying manual pressure,
connected via shafts 44 to a central disc shaped pressure pad 41 and an
annular pressure pad 42. The pressure pads 41, 42 are engaged with bungs
/ plunger seals 31, 13, respectively, of the annular barrel chamber 7 and of
the cartridge 30.
[0210] At the front of the barrel 1, a foaming unit 50 is fitted to the luer
nozzle 5. The foaming unit comprises a stack of mesh elements with
microscopic perforations. The foaming unit will be described in more detail
below in relation to Figures 11, 12 and 13.
[0211] In use, the plunger stem 40 is depressed either manually or in a
syringe driver such as the one shown schematically in Figure 8 and discussed
below. The syringe with partly depressed plunger stem and foaming unit
fitted is shown in Figure 6. The plunger seals 13, 31 in the annular carbon
dioxide chamber and in the chamber defined within the cartridge are
advanced as the plunger stem is depressed, thereby driving carbon dioxide
and polidocanol solution through the apertures 12 and the orifice 9. Mixing of
the gas and liquid takes place in the region 15 in front of the orifice 9
where
the annular gas flow interacts with the liquid flow. The mixture then proceeds
as indicated by arrow A in Figure 6 through the syringe nozzle 5 into the
foaming unit 50 where the gas and liquid are passed through microscopic
perforations of average dimension 5micron to create a fine foam or foam with
an average bubble size of around 100micron.
[0212] Figure 7 shows an alternative syringe-based design. A syringe
barrel 101 houses twin parallel gas and liquid chambers 107, 114 which
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receive respective cartridges 170, 120 of the type shown In Figure 2 with
resilient bungs 171x,171 b, 121a,121 b at each end. The'gas chamber 107
contains cartridge 170 which Is filled with substantially 100% pure carbon
dioxide-at substantially atmospheric pressure. The liquid chamber 114
contains cartridge 120 which is filled with 1 %: poiidocanoi solution.
[0213] At the rear end of the barrel 101 a plunger stem is fitted,
comprising a disc 143 for applying manual_pressure, connected via shafts 144
to two disc shaped pressure pads 141, 142 received within the gas and liquid
chambers 107,114; respectively.
[0214] At the front end of the syringe barrel is an end wall 104 from
which projects a cylindrical hub 1:16 with a nozzle 105 at the end. Within the
hub 116 Is a mixing chamber or mixing region 115, In this region are located
static mixing fins 117. Located at the front of the chambers 107, 114 are
hollow needle-like members 118, 119 respectively, each with a point I 18a,,
119a facing into the respective chamber. Each needle-like member is
contoured to lie along the front face of Its respective..chamber and to extend
Into the mixing chamber 1 15.
(0215] Fitted to the, nozzle. 106 of the syringe is a foaming unit 50 of
similar design to that used in the device, of Figures 1 to 6. The foaming unit
will be described more fully below with reference to f=igures 11-13.
[0216] The syringe is supplied with cartridges 120, 170 pre-fitted. A clip
129 prevents depression of the plunger stem 140 until the clip Is removed
immediately prior to use. When it is desired to use the syringe, the clip 129
is
removed and the plunger manually depressed so that the cartridges 120, 170i
which are a.snug fit In their respective chambers 114, 107, are advanced, into
contact with the needle elements 119,118 respectively. Further depression
of the plunger stern 140 causes the needle points 119a, 118a to penetrate the
resilient bungs 121a, 171a at the front of the cartridges, thereby opening a
communication channel between:the interior of the cartridges and the mixing
49.
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chamber 11&
[02171 Further depression of the plunger stem 140 causes carbon
dioxide and polidocanol solution to flow together into the mixing chamber, in
a
ratio predetermined by the cross-sectional areas-of the cartridges. Fins 117
in the mixing chamber ensure that the gas and liquid are thoroughly mixed
prior to entering, the=foaming unit 50 where the-liquid: and gas is converted
Into
a; foam.
10218]0hen treating a patient; the clinician would go through the
above steps. and ensure that consistent foam ]s:being discharged from the
foaming unit 50. Pressure. is then released from the, plunger stem 140 and a
line from a cannula, which has previously been Inserted Into a veinto be
treated, Is connected by a .standard luer fitting to the exit of the foaming
unit.
Pressure would then be applied again to the plunger stem 140 to produce
foam and at the same time Inject it through the line and cannula and into the
patient's vein.
[0219) The. exact properties of the foam will depend; to some extent on
the speed at which the plunger stem 140 is depressed. For this reason it' is
preferable that a syringe driver is used to administer the foam. A syringe
driver Is shown schematically in Figure 8, with the syringe of Figure 7 fitted
in
It. The driver 200 comprises .a base 201, syringe clamp 202 and motor 204
fitted In a motor mounting 203, The motor 204 Is coupled via a coupling 209
to a: drive shaft 206 having an external thread; 210. Received on the drive
Shaft is annular member 207 having an internal thread 211: engaged with the
external thread 210 of the drive shaft. From the annular member 207 extends
a driving member 208 which bears on the plunger stem 140 of the syringe which
Is clamped in the syringe clamp 202.
[0220] The motor Is connected to a DC power supply 212, has a speed
calibration control 209 for setting the correct drive speed, and also an
on/off
control 205.
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[0221] In use, the clinician would remove the clip 119 from the syringe
of Figure 7, depress the plunger stem 140 to the point where consistent foam
is being produced, then insert the syringe into the driver and connect up to a
line 80 previously installed in a patient's vein. The speed of the motor 204
would previously have been calibrated to a speed appropriate for the syringe
being used. The clinician then has control of the delivery of foam to the
patient by means of the on/off switch.
[0222] As short a line as possible is used, so that a very small quantity
of foam resides in the line when the motor is switched off. In this way, it is
ensured that almost all the foam delivered to the patient has been generated
only a few moments previously and has had very little opportunity to degrade.
[0223] Figures 9 and 10 show an alternative embodiment 300 of foam
generating and dispensing device. This embodiment is based on a bag 301
of metal / plastics laminate material. In the bag are located chambers 302,
303 separated by ultrasonically welded seams 310. The chambers 302, 303
contain carbon dioxide and 1 % polidocanol solution respectively. The
chambers are disposed in parallel along substantially the whole length of the
bag, and the cross sections of the chambers, when filled, is selected so as to
ensure a correct gas/air mix as with the syringe embodiments. Each chamber
302, 303 has a channel 304, 305 leading to a mixing region or mixing
chamber 306 defined within a housing 307. On the front of the housing 307 is
a luer nozzle 308, to which is fitted a foaming unit 50 as with previous
embodiments. Within the mixing chamber 306 are located mixing fins 311.
[0224] At the rear of the bag 301 is a relatively stiff rod 309. In use, the
bag 301 is rolled around the rod 309 to expel gas and liquid from the
chambers 302, 303 respectively. As with previous embodiments, the gas and
liquid enter the mixing chamber where they are well mixed before entering the
foaming unit 50 and being converted to foam of preset density.
[0225] As with the other embodiments, the bag is preferably used with
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a driver device such as is shown schematically in Figure 10. In Figure 10 the
bag 301 can be seen in side view, held in place on a movable carriage 321,
slidably mounted on a base plate 320. The rear of the bag 301 is clamped by
a bag clamp 322 at the rear of the carriage 321; the rod 309 in this situation
serves to help prevent the bag slipping through the clamp. The mixing
chamber housing 307 at the front of the bag is clamped in a mixing chamber
clamp 323 at the front of the carriage 321.
[0226] To set up the driver, the carriage, complete with bag, is slid
sideways under a roller 324 mounted on the base plate 320. In order to do
this, the bag is manually depressed at the rear end, adjacent the rod 309 to
allow it to fit under the roller 324.
[0227] The roller 324 is driven by an electric motor 325 supplied from a
DC power supply 326. The speed of the motor may be calibrated using
speed control 327 and stopped and started using on/off switch 328.
[0228] On starting the motor, the roller rotates in the sense indicated by
arrow B, causing the carriage, complete with bag, to slide under the roller.
Gas and liquid contained in the bag is thereby forced through the mixing
chamber 306 and foaming unit 50, and out of an exit of the foaming unit.
[0229] As with the previous embodiments, the clinician would ensure
that consistent foam is being produced before connecting up a line 80 to a
cannula installed in a patient's vein.
[0230] Referring now to Figures 11 to 13, the foaming unit comprises
four mesh elements, each comprising a ring 51 having a mesh 52 secured
across it. The mesh has perforations of diameter approximately 5micron.
Each mesh element has male and female sealing surfaces 53, 54
respectively - these are best seen in Figure 12.
[0231 ] Figure 13 shows four mesh elements stacked together such that
the male sealing surface of one element engages the female surface of the
element next to it. The elements are retained in housing 55 having a socket
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half 56 and a nozzle half 57. Between these halves of the housing, the mesh
elements are retained under pressure, with the sealing surfaces 53, 54
engaging with each other and with the interior of the housing 55 at each end.
In this way a good seal is created between the mesh elements, so that all flow
through the foaming unit must pass through the mesh.
[0232] The socket end 56 of the housing is formed with a standard luer
socket 58 which, in use, fits over the luer nozzle output of the various
devices
described above. The nozzle end 57 of the housing incorporates a standard
luer nozzle 59 onto which a medical line having a standard luer socket may
be fitted.
[0233] Alternatives to the mesh elements described are contemplated:
anything which provides pores, perforations, interstices, etc with a dimension
in a direction approximately transverse to the direction of flow of between
0.1 micron and 100micron may be suitable. Examples might include a fabric,
perforated screen or sinter.
[0234] The following examples are provided in support of the inventive
concepts described herein.
[0235] The present invention will now be described further by way of
illustration only by reference to the following Figures and Examples. Further
embodiments falling within the scope of the invention will occur to those
skilled in the art in the light of these.
[0236] Example 1
[0237] 10 patients were treated for varicose veins by injection of foam
made with 1 % polidocanol solution and a gas mix consisting essentially of 7-
8% nitrogen and the remainder carbon dioxide (about 22%) and oxygen
(about 70%).
[0238] The procedure involved the injection of up to 30ml of foam
(25.5ml gas) into the thigh section of the greater saphenous vein. 4-chamber
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cardiac ultrasound examinations were conducted on all the patients to test for
bubbles reaching the heart. Bubbles were observed in the right atria and
ventricles of all 10 patients examined. In general, bubbles appeared several
minutes following injection of the foam and continued until the ultrasound
recording was stopped about 40 minutes after injection.
[0239] In one patient, microbubbles were observed in the left atrium
and ventricle. This patient was subsequently confirmed to have a patent
foramen ovale.
[0240]
[0241] Example 2
[0242] The objective of this experiment was to investigate the nature of
the residual bubbles that pass into the heart following injection into the
saphenous vein of polidocanol foam made with different gas mixtures.
[0243] An anaesthetised female hound dog weighing 26 kg was
injected with foam containing polidocanol formulated with varying gas mixes.
Residual bubbles were monitored in the pulmonary artery using
transoesophageal echocardiogram (TEE). Residual bubbles visualised on
TEE were sampled from the pulmonary artery through a wide-bore catheter.
These blood samples were analysed for the presence of residual bubbles
using light microscopy and ultrasound.
[0244] Three different compositions of foam were used, as follows:
[0245] 1 % polidocanol and air
[0246] 1 % polidocanol and a gas mix consisting of 7-8% nitrogen and
the remainder carbon dioxide and oxygen
[0247] 1 % polidocanol solution and a gas mix comprising less than 1 %
nitrogen and the remainder carbon dioxide and oxygen.
[0248] The TEE output was videotaped and subsequently analysed.
For all three compositions, bubbles reached the pulmonary artery in sufficient
quantity to cause a substantially opaque image. It is believed that the
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threshold bubble density required to produce such an image as quite low, and
therefore this image in itself did not provide useful data. The time taken for
the occluded image to revert to a steady state background image was
believed to be approximately indicative of the length of time taken for all or
most the bubbles to have dissolved into the bloodstream. The TEE was very
sensitive (showing activity even when saline was injected as a control); for
this reason exact end points were difficult to determine. However, the
following estimates have been made of the time period from opacification of
the image to decay down to a background level.
[0249] 4 minutes
[0250] 2 minutes
[0251] 20 seconds.
[0252] In addition to the TEE analysis, observations were made of
samples of blood drawn from the pulmonary artery for each foam during the
period when the TEE image was substantially opaque. The results of these
observations were as follows.
[0253] As soon as the sample was taken, a considerable volume of
bubbles was observed in the syringe. When the syringe was held with its
longitudinal axis horizontal, a continuous strip of bubbles was observed
extending substantially the full length of the 20m1 syringe.
[0254] Initially on taking the sample no bubbles were observed in the
syringe, but after a few seconds, with the syringe in the horizontal position,
a
line of bubbles appeared which was thinner than the line observed for foam A.
[0255] After taking the sample and holding the syringe in the horizontal
position, no bubbles were observed for a period of a minute or more.
Gradually, a thin line of bubbles began to appear along the top of the
syringe.
[0256] It was not possible to measure the bubbles, but they appeared
to be smaller for composition C than for composition B, with the bubbles from
composition B in turn smaller than those from composition A.
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[0257]
[0258] Example 3
[0259]
[0260] In vitro experiments were conducted to determine the
absorption of foam made with different gases in fresh human venous blood.
[0261 ] A 20ml polypropylene syringe barrel was prepared by
puncturing its side wall with a relatively large hypodermic needle to make a
hole approximately 1 mm in diameter. This hole was then covered by
securing a piece of clear flexible vinyl sheet over it with clear adhesive
tape.
A small magnetic stirrer element was introduced into the syringe barrel and
the plunger then replaced. 20ml of human venous blood was then with
withdrawn in the usual manner from a human subject using the specially
prepared syringe fitted with a hypodermic needle.
[0262] The hypodermic needle was removed and the syringe then
placed on a magnetic stirrer unit so that the magnetic element in the syringe
thoroughly agitated the blood. The Luer nozzle of the syringe was then
connected to a 50cm piece of manometer tubing which was arranged
horizontally and left open at one end. The manometer tubing was secured
against a scale.
[0263] A 0.5m1 measuring syringe with a fine pre-fitted needle was then
filled with foam made from 1 % polidocanol solution and air. The density of
the foam was 0.13g/ml ( 0.03g/ml), the liquid component making up
approximately 13% of the total volume of foam ( 3%).
[0264] The needle of the 0.5ml syringe was then introduced through
the vinyl sheet on the side wall of the 20m1 syringe. A small volume of blood
was found to have entered the manometer tubing and the position of the
distal end of this column of blood was noted against the scale. The 0.5ml
aliquot of foam was then injected quickly and simultaneously a timer started
(t0). As the foam displaced blood in the 20ml syringe, the column of blood
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from the 20m1 syringe was displaced into the manometer tubing and the
distance along the tubing reached by the distal end of the blood column was
noted against the scale. The scale itself comprised spaced marker lines
equally spaced at about 1cm intervals. It was determined that a distance of
45 intervals on this scale corresponded to an internal volume of in the
manometer tubing of approximately 0.5m1.
[0265] As the gas in the foam started to be absorbed by the blood, the
blood in the manometer tubing started to recede back towards the syringe.
After the column appeared to have stopped moving, the timer was stopped
(tF). The position of the distal end was again noted.
[0266] This experiment was then repeated for a foam of the same
density but made with oxygen gas ("medical grade" purity - 99.5% minimum).
[0267] The experiment was repeated again but this time oxygen gas
from a cylinder of medical grade oxygen was introduced directly into the 0.5ml
syringe instead of foam.
[0268] The results of these three tests ate presented below in Table 1
Table 1
Start Position Position Absorbed Liquid Unabsorbed
position of blood tF of blood volume at Volume gas
Test Foam/gas of blood at to (seconds) at tF tF (ml) in foam
("xõ) ("y") ("Z") 0.5 -z (ml) ml %
(Y-X)
Air 0.13 x
1 foam 2 47 80* 40 0.08 0.5 0.35 81%
= 0.07
Oxygen 0.13 x
2 foam 4 48 140 11 0.42 0.5 0.01 2%
= 0.07
Oxygen
3 gas 2 47 140 5.5 0.46 nil 0.04 8%
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[0269] *No further movement of the blood column was observed after
80 seconds.
[0270] The experimental error in this example is unfortunately too great
to conclude whether there is or is not a residual volume of gas for the oxygen
gas or oxygen foam, although clearly the great majority at least of the gas is
absorbed. There will have been a small percentage of nitrogen in the gas,
from the oxygen cylinder which is only 99.5% pure, and possibly also
introduced during the experiment. Diffusion of nitrogen into the bubbles from
the blood is also a possibility, as discussed above, and some nitrogen may
have been introduced inadvertently during the procedure.
[0271] In this experiment, the air foam test was only observed for a few
minutes after tF. However, further experiments have been conducted by the
inventors, the results of which are not formally recorded here, involving foam
with a percentage of nitrogen. A 20ml syringe of fresh human venous blood,
as in the above experiments, was injected with a 0.5ml aliquot of a foam
containing a percentage of nitrogen. The contents of the syringe were
agitated as above and a period of 24 hours allowed to elapse. An easily
visible volume of bubbles remained in the syringe.
[0272]
[0273] Example 4 - preparation of ultra-low nitrogen canister
[0274]
[0275] An anodised aluminium canister with an open top was filled with
water. The canister was then immersed in a bath of water and inverted. A
line from a pressurised cylinder of oxygen gas was then introduced into the
water bath and the supply of oxygen turned on, thereby flushing the line of
any air. A canister head assembly comprising a valve, dip tube and mesh
stack unit was then immersed in the water bath and connected to the oxygen
line for a few seconds to purge air from the assembly.
[0276] The oxygen line was then introduced into the inverted canister
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until all water had been displaced from the canister. The line was then
removed from the canister and the previously purged head assembly quickly
clamped over the top of the canister thereby sealing the canister. The
canister was then removed from the water bath with the head assembly still
clamped against it; the head assembly was then secured to the canister using
a standard crimping technique.
[0277] The canister was then pressurised to about 8 bar absolute
pressure by connecting the canister valve to a regulated oxygen line for 1
minute. The pressure as then relieved by opening the valve until the pressure
in the canister was just above 1 bar absolute; a pressure gauge was applied
to the valve intermittently during the pressure release operation to ensure
that
the canister pressure did not drop all the way down to 1 bar absolute. This
was done to avoid the possibility of atmospheric air seeping into the
canister.
[0278] The canister was then pressurised again up to about 8 bar
absolute and the pressure release operation repeated. This process was
then repeated a third time, with the final canister pressure being from 1.1 to
1.2 bar absolute.
[0279] 18m1 1 % polidocanol solution was then introduced through the
canister valve using a syringe with all air pockets, including any air in the
luer
nozzle, removed. The canister valve was then connected to a carbon dioxide
cylinder and pressurised to 2.2 bar absolute. Then the oxygen line was again
connected to the valve and the pressure increased to 3.6 bar absolute.
[0280] Table 2 below shows the expected result from the oxygen
pressurising and depressurising cycles, assuming 100% pure oxygen in the
cylinder and assuming that despite the precautions taken 1 % of the gas in the
canister after the initial oxygen filling procedure is nitrogen. The worst
case is
assumed for the canister pressure values, namely 1.2 bar absolute ("bara")
and 7.6 bara.
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Table 2
N2 partial pressure Canister pressure %N2
(bara) (bara)
Start 0.012 1.2 1%
1St cycle 0.012 7.6 0.16%
0.00189 1.2 0.16%
2" cycle 0.00189 7.6 0.02%
0.000299 1.2 0.02%
P cycle 0.000299 7.6 0.00%
0.0000472 1.2 0.00%
[0281] As can be seen the percentage of nitrogen drops down to zero,
calculated to two decimal places, after the three oxygen pressure/release
cycles.
[0282] The oxygen cylinder used in the above process was a standard
medical grade oxygen cylinder supplied by B.O.C. and specified at 99.5% or
greater purity. The carbon dioxide cylinder used was so called "CP Grade"
from B.O.C. which has a purity level of 99.995%.
[0283] Working to two decimal places, the impurity (which will be
mainly nitrogen) arising from the initial filling procedure should be reduced
to
zero after three pressure/release cycles. Similarly the impurity level in the
canister from the carbon dioxide cylinder can be considered zero to two
decimal places, since the purity of the source was 99.995% and only
approximately one third of the gas in the finished canister was carbon
dioxide.
[0284] The inventors will perform further experiments along the above
lines using oxygen and carbon dioxide sources of higher purity. The following
cylinder oxygen is readily available from B.O.C.:
[0285] "Medical grade" 99.5% purity (as used in the above procedure)
[0286] "Zero grade" 99.6% purity
[0287] "N5.0 grade" 99.999% purity
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[0288] "N5.5 grade" 99.9995% purity
[0289] "N6.0 grade" 99.9999% purity
[0290] In each case the impurity is mainly nitrogen.
[0291] The following cylinder carbon dioxide products are readily
available from B.O.C. They have the following specifications:
[0292] "CP grade N4.5" 99.995% purity (as used in the above
procedure)
[0293] "Research grade N5.0" 99.999% purity.
[0294] It will be appreciated that repeating the procedure described
above using "Zero grade" oxygen would result in a finished canister having
maximum impurity (which will be mainly nitrogen) of 0.4%.
[0295] Of course the number of pressure/release cycles may be
increased in order further to reduce the theoretical maximum impurity if the
oxygen and carbon dioxide sources were 100% pure. It is a simple
calculation to show the number of cycles necessary to reduce the maximum
percentage impurity level to zero, calculated to 3, 4 or 5 decimal places.
Provided the canister pressure never drops to or below 1 bar absolute and
provided the lines from the oxygen and carbon dioxide cylinders are flushed
through with gas prior to attachment to the canister valve, there is no reason
to assume that any significant impurity will enter the canister during the
pressure/release cycles.
[0296] A refinement of the procedure to reduce further any opportunity
for impurity to enter would be to introduce the polidocanol solution
immediately after initial flushing. In this way, any air/nitrogen introduced
with
the polidocanol will be eliminated during the subsequent pressure/release
cycles.
[0297] A further refinement of the technique might be to maintain the
water bath in an agitated state using a magnetic stirrer, under a continuously
refreshed oxygen atmosphere for 24 hours. In this way, any dissolved
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nitrogen in the water bath should be eliminated and replaced with dissolved
oxygen. Filling the canister from this oxygenated water bath should, it is
postulated, remove the water bath as a possible source of nitrogen impurity.
[0298] It is envisaged that five, ten, twenty or even 100
pressure/release cycles could be performed.
[0299] In this manner, using appropriate sources of oxygen and carbon
dioxide as detailed above, it will be possible to make a canister charged with
polidocanol and an oxygen and carbon dioxide mix having a percentage
impurity of 0.005% or less (mainly nitrogen) using CP grade carbon dioxide or
0.001 % or less using research grade carbon dioxide. It should also be
possible to make a polidocanol and oxygen canister with a percentage
impurity of nitrogen gas of 0.0001 % or less using N6.0 grade oxygen.
[0300] It will of course be appreciated that the production of canisters
in this way having a somewhat higher minimum nitrogen level is not difficult
and may be achieved, for example, by reducing the number of
pressure/release cycles.
[0301] It will also of course be appreciated that substitution of
polidocanol by an alternative liquid component would be a trivial matter.
[0302]
[0303] Example 5 - preparation of ultra-low nitrogen canister
[0304]
[0305] The inventors are at present developing a procedure for large
scale manufacture of ultra-low nitrogen canisters, using a similar
methodology. In this procedure, two canisters are manufactured, one
containing oxygen at 5.8 bar absolute and the other carbon dioxide and
polidocanol solution at about 1.2 bar absolute. In use, the C02/polidocanol
canister is pressurised immediately prior to use by connecting it to the
oxygen
canister. This is described in WO 02/41872-A1 [CDE10].
[0306] There is therefore a separate manufacturing procedure for the
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oxygen and carbon dioxide / polidocanol canisters. However, it will be
apparent that either procedure is applicable to production of a single
canister
product containing polidocanol and oxygen, carbon dioxide or a mix of the
two.
[0307] The procedure will be described first for an oxygen canister,
which is simply an anodised aluminium canister with a standard valve
assembly in the top. Prior to fitting the valve assembly, the canister is
first
flushed with oxygen gas by inserting an oxygen line into the open top of an
upright cylinder for 10 seconds. The line is then withdrawn. At this stage not
all the air will have been eliminated and it is believed that the nitrogen
impurity level is around 5% or 6%; this has not been measured specifically,
but has been deduced from the measured impurity level at a later stage in the
procedure (see below). It is not believed that flushing the canister for a
longer
period would substantially change this value for nitrogen gas impurity.
[0308] The valve assembly is then loosely fitted and a filling head
brought into engagement around the top of the canister and valve assembly
so as to make a gas-tight seal against the canister wall. Connected to the
filling head is a line for oxygen. The canister is then brought up to a
pressure
of approximately 5.5bar absolute (bara). Nitrogen gas impurity at this stage
has been measured by standard gas chromatography techniques to be about
1%.
[0309] At one stage it was thought to be acceptable to have the
nitrogen impurity level at around 1 %, but following the results of the
clinical
trial (Example 1), it has been determined that a lower nitrogen content is
desirable. For this reason, further steps have been added to the procedure,
as follows.
[0310] Maintaining the seal between the canister and filling head, the
contents of the canister are exhausted via the filling head until the pressure
in
the canister is just over 1 bara. As with Example 4 above, this is to prevent
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any potential ingress of atmospheric air through the seal.
[0311] Maintaining the seal between the canister and filling head, the
pressure is then increased again to about 5.5 bara and again this pressure is
released down to just over 1 bara. The canister is then brought up to its
final
pressure of 5.5bara 0.4 bara. At this stage, the nitrogen gas impurity
measured by gas chromatography is about 0.2%.
[0312] It will be appreciated that each of the pressure/release cycles
should reduce the impurity due to residual air/nitrogen by a factor of about 5
assuming no leakage. It is reasonable to assume no leakage since a positive
pressure is always maintained in the canister. Assuming a 100% pure source
of oxygen, the theoretical nitrogen impurity after these three
pressure/release
cycles should be around 0.05%. Since the measured nitrogen level is around
0.2%, there is apparently either impurity in the line or nitrogen is entering
the
sample during the measuring process. It can at least be concluded that the
impurity level is 0.2% or better.
[0313] It will be appreciated that polidocanol solution, or any other
liquid sclerosing agent, could be added into the canister during the above
procedure and the standard valve and dip tube could be replaced with a unit
including foam generating means such as a small aperture mesh. In the final
step, the pressure in the canister may be brought up to whatever is required,
e.g. around 3.5 bara. In this way, a final pressurised canister product
containing sclerosant and substantially pure oxygen could be made.
[0314] At present, the effects, including possible oxidising effect, of
storing polidocanol solution under pressurised oxygen are not fully
understood. Therefore, it is preferred at present to have a two canister
system in which the polidocanol solution is stored under carbon dioxide
and/or nitrogen.
[0315] In previous versions of the product (as used in Example 1), the
gas mix in the polidocanol canister was 25% nitrogen and 75% carbon
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dioxide. The nitrogen was present in order to reduce the deleterious effect of
the highly soluble carbon dioxide on the stability of the foam. In order to
minimise both the carbon dioxide and the nitrogen content of the foam, this
canister was maintained at 0.5 bara. This meant that, when the canister was
connected to the oxygen canister and the final pressure raised to about 3.5
bara, the nitrogen content reduced to around 7%.
[0316] It was then realised by the inventors that (1) the canister needed
to be maintained at above atmospheric pressure to avoid the risk of
contamination and (2) the percentage of nitrogen was too high. A new design
of can was produced in which the foam generating mesh has smaller
apertures - 5 micron instead of 20 micron. Although it was previously thought
that differences in size at this level would not have a significant effect on
the
foam, it was in fact surprisingly found that this reduction in mesh pore size
was just sufficient to compensate for the increased percentage of carbon
dioxide which resulted from having substantially pure carbon dioxide in the
canister and also from maintaining it at just over 1 bara instead of 0.5 bara.
[0317] Using a polidocanol canister of this design, and an oxygen
canister as described above which is pressurised only once, the resulting
foam had a nitrogen impurity of around 1-2%.
[0318] The current procedure is to insert a carbon dioxide line into the
open top of a metal anodised canister for 10 seconds. The line is then
withdrawn. At this stage not all the air will have been eliminated and it is
believed that the nitrogen impurity level is around 5% or 6%. It is not
believed
that flushing the canister for a longer period would substantially change this
value for nitrogen gas impurity.
[0319] 18m1 of 1 % polidocanol solution is then introduced into the
canister, a carbon dioxide line reintroduced and the canister flushed again
for
a few seconds.
[0320] The head assembly, including dip tube, valve and foam
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generating mesh unit, is then loosely fitted and a filling head brought into
engagement around the top of the canister and valve assembly so as to make
a gas-tight seal against the canister wall. Connected to the filling head is a
line for carbon dioxide. The canister is then brought up to its pressure of
approximately 1.2 bara. Nitrogen gas impurity at this stage has not yet been
measured but is expected to be in the region of 0.8%.
[0321] The final nitrogen impurity of a foam generated from the
charged polidocanol canister after it has been connected to the oxygen
canister to bring it up to about 3.5 bara, is given by:
[0322] (0.8 x 1.2 + 0.2 x 2.3) / 3.5 = 0.4%
[0323]
[0324] Example 6
[0325]
[0326] A unit was prepared comprising a housing with ports at each
end formed as standard luer connections. Within the housing was an internal
pathway between the ports in which pathway four mesh elements were
installed such that flow between the ports was required to flow through the
meshes. The meshes had 5 micron apertures.
[0327] 8ml of 1 % polidocanol solution was drawn up into a standard
20ml syringe and this syringe then fitted to one port of the mesh stack unit
described above. A second 20ml syringe was then taken and 12ml of air
drawn up into it before fitting it to the other of the two ports on the mesh
stack
unit. The internal volume of the mesh stack unit was measured and
determined to be essentially negligible for these purposes, being 0.5ml or
less.
[0328] The air and polidocanol solution was then shuttled back and
forth between the syringes as fast as possible by hand for one minute. The
number of passes achieved was 15.
[0329] The resulting product was a white liquid of homogeneous
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appearance with no visible bubbles. A sample of this liquid was analysed for
bubble size (see Example 9 below) and the results tabulated below (Table 2).
Table 2
Bubble diameter ( ) Number of bubbles Cumulative freq. (%) Frequency (%)
0-15 1420 28.4 28.4
15-30 1293 54.3 25.9
30-45 1230 78.9 24.6
45-60 819 95.3 16.4
60-75 219 99.7 4.4
75-90 15 100.0 0.3
90-105 0 100.0 0.0
105-120 0 100.0 0.0
120-135 0 100.0 0.0
Totals: 4996 100.0
[0330]
[0331] Example 7
[0332]
[0333] A similar experiment to Example 6 above was performed with a
housing containing 4 mesh units each comprising a 5 micron mesh. This
time, 10ml of 1 % polidocanol solution was drawn up in one 20ml syringe and
10ml of air drawn up in the other. The air and polidocanol were shuttled back
and forth as fast as possible by hand for 2 minutes; 27 passes were achieved.
[0334] The resulting product was a white liquid of homogeneous
appearance with no visible bubbles. A sample of this liquid was analysed for
bubble size (see Example 9 below) and the results shown in Table 3 below.
[0335]
Table 3
Bubble diameter ( ) Number of bubbles Cumulative freq. (%) Frequency (%)
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0-15 2387 47.8 47.8
15-30 1293 73.7 25.9
30-45 969 93.1 19.4
45-60 309 99.2 6.2
60-75 32 99.9 0.6
75-90 4 100.0 0.1
90-105 2 100.0 0.0
105-120 0 100.0 0.0
120-135 0 100.0 0.0
Totals: 4996 100.0
[0336]
[0337] Example 8
[0338]
[0339] A similar experiment to Examples 6 and 7 above was performed
with a housing containing 4 mesh units each comprising an 11 micron mesh.
8m1 of 1 % polidocanol solution was drawn up in one 20m1 syringe and 12m1 of
air drawn up in the other. The air and polidocanol were shuttled back and
forth as fast as possible by hand for 1 minute; 25 passes were achieved.
[0340] The resulting product was a white liquid of homogeneous
appearance with no visible bubbles. A sample of this liquid was analysed for
bubble size (see example 9 below) and the results shown in Table 4 below.
Table 4
Bubble diameter ( ) Number of bubbles Cumulative freq. (%) Frequency (%)
0-15 620 12.4 12.4
15-30 753 27.5 15.1
30-45 1138 50.3 22.8
45-60 1279 75.9 25.6
60-75 774 91.4 15.5
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75-90 331 98.0 6.6
90-105 85 99.7 1.7
105-120 15 100.0 0.3
120-135 1 100.0 0.0
Total: 4996 100.0
[03411
[0342] Example 9: Bubble Sizing Technique
[0343]
[0344] The bubble sizing technique used to measure the bubble size
distribution of the foams from Examples 6 to 8 above comprises computer
analysis of the image of the bubbles though a microscope. A small sample of
the foam is deposited on a specially prepared slide which has spacers 37
microns high mounted on each side. A further slide is then carefully
positioned on top of the sample and spacers, thereby spreading the sample
into a layer of 37 micron thickness. A digital image of part of the 37 micron
layer of bubbles is then recorded and processed: the bubbles appear as rings
in the image, the ring representing the outermost diameter of the bubble.
Each bubble is individually identified and numbered, and its diameter
calculated. For bubbles over 37 microns in diameter it is assumed that the
bubble has been flattened to some degree causing the diameter of the ring in
the image to be larger than the diameter of the undeformed bubble. An
algorithm for calculating the original diameter of the undeformed bubble is
applied. For bubbles 37 microns and under, it is assumed that the bubble has
floated up against the underside of the upper slide and is undeformed. From
visual inspection of the digital image, this does not appear to be an
unreasonable assumption since overlapping bubble images are either absent
completely or are very rare. Nevertheless it is intended to repeat the
experiments using a set of slides with a 10micron gap and suitably amended
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software, once these things have been developed, so that substantially all the
bubbles will be flattened between the slides.
[0345]
[0346] Example 10
[0347]
[0348] Examples 6, 7 and 8 above are repeated using the following
method.
[0349] Polidocanol solution is drawn up into a 20m1 syringe as
described in Examples 6, 7 and 8, ensuring that excess solution is drawn up
and then solution dispensed with the nozzle pointed upwards, until the
appropriate volume of polidocanol solution is left. In this way any air voids
in
the syringe, particularly in the nozzle, are removed.
[0350] The polidocanol-filled syringe is then connected to the mesh
unit, the assembly oriented with syringe pointing upwards, and the mesh unit
filled with solution, eliminating all air bubbles.
[0351 ] A line from a cylinder of medical grade oxygen (99.5% purity) is
connected to the luer connector of a 20m1 syringe with the plunger removed.
The oxygen line and syringe barrel and luer connector are then flushed for 10
seconds with oxygen from the cylinder. The oxygen line is then removed,
keeping the supply of oxygen turned on, and the syringe plunger inserted into
the barrel and the plunger depressed. The oxygen line is then re-attached to
the syringe luer and the pressure of the oxygen allowed to push the syringe
plunger back to fill the syringe with oxygen.
[0352] The oxygen syringe is then immediately connected to the mesh
unit and the foam generating procedure described in Examples 6, 7 or 8
carried out.
[0353]
[0354] Example 11
[0355] A syringe and mesh unit filled with polidocanol solution as
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described in Example 10 above are placed in a collapsible "glove box" (a
sealable container with integral gloves incorporated into the container wall
to
allow manipulation by a user of the contents of the container). A further,
empty syringe is also placed in the glove box. The box is then sealingly
connected to vacuum source and thereby collapsed such that substantially all
air is removed. The vacuum source is then replaced by a source of 99.995%
pure oxygen and the glove box filled with oxygen from this source; the oxygen
supply is maintained and a small vent is opened in the wall of the glove box
opposite the point of entry of oxygen. The procedure described in Example
10 above for filling the empty syringe with oxygen is then followed, using the
99.995% pure oxygen supply line within the glove box. The procedure
described in Examples 6, 7 and 8 is then carried out to generate foam.
[0356]
[0357] Example 12
[0358]
[0359] A polidocanol syringe and mesh unit are prepared as in
Example 10 above. A syringe is immersed in a tank of water and the plunger
removed. Once the syringe barrel is completely full of water with no air
pockets, a stopper is secured over the luer nozzle. The syringe barrel is held
with the nozzle pointing upwards and a line from a 99.9999% pure oxygen
cylinder is first purged, then introduced into the syringe barrel. When all
water is replaced by oxygen (taking care that the water in the nozzle is
displaced), the plunger is inserted and the syringe removed from the water
tank. The procedure of Example 10 is then followed to connect the syringe to
the mesh unit and make foam.
[0360] As with Example 4 above, this procedure could be refined by
storing the water tank under a continually refreshed atmosphere of 99.9999%
pure oxygen for 24 hours prior to filling the syringe.
[0361]
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[0362] Example 13
[0363]
[0364] In a modification of Examples 10-12, the mesh unit can be
replaced with a simple connector or three way valve and in all other respects
the technique can remain the same, with the possible exception of requiring
more passes to make acceptable foam. The aperture in a standard connector
or three way valve, through which the gas and liquid are passed, would be
about 0.5mm to 3mm in its largest dimension. By repeatedly passing the
liquid and gas through this aperture it is still possible to obtain a useful
foam,
though with bubble sizes considerably larger than those obtained by the
methods of Examples 6 to 12. This technique is commonly known as the
"Tessari" technique. The inventors have experimented with the Tessari
technique and found that the size and distribution of bubbles varies widely
according to the ratio of gas to air and also the speed and number of passes
of the gas and liquid through the aperture. The average bubble size for a
Tessari foam has been reported in the literature to be around 300micron. The
best that the inventors have managed to achieve using the Tessari technique
is a foam with an average bubble size of around 70micron, though to do this
the ratio of liquid to gas had to be increased to about 40% liquid, 60% gas.
[0365] In this example, the Tessari technique can be adapted to make
a foam of whatever density and bubble size is desired, within the limitations
described above, but using gas with a very low percentage of nitrogen
impurity.
[0366]
[0367] Example 14
[0368]
[0369] A canister was prepared of the type described in
W000/72821-A1 having a dip tube and a standard valve assembly provided
with a pair of small air inlet apertures, together with a mesh stack unit
having
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a 5micron aperture size. The size of the apertures in the valve was enlarged
slightly compared with the valve arrangement described in W000/72821-A1
(which is designed to produce a foam of density between 1.1g/ml and
1.6g/ml). The purpose of this modification was to increase the proportion of
liquid to gas in the mixture passing through the mash stack.
[0370] The canister was filled with 18ml of 1 % polidocanol solution and
pressurised with a mixture of oxygen, carbon dioxide and nitrogen. A foam
was then dispensed.
[0371 ] This procedure was repeated for different sizes of valve
aperture and a number of foams produced, all having the appearance of a
white liquid and densities in the range 0.3 to 0.5g/ml. Bubble size analysis
was performed for each of these foams, which showed the average bubble
size in the region of 50 to 80micron diameter.
[0372]
[0373] Example 15
[0374]
[0375] The above experiment was repeated but with the length and
diameter of the dip tube adjusted rather than the size of the apertures in the
valve unit. It was necessary to increase the volume of liquid in the canister
to
ensure that the shortened dip tube reached the liquid level in the canister.
It
was possible to produce the same type of foam as described in Example 6
above.
[0376]
[0377] Example 16
[0378]
[0379] The inventors envisage reproducing the above experiments
using a pure oxygen or oxygen and carbon dioxide formulation having
nitrogen impurity levels as described above. The same techniques as those
described in Examples 4 and 5 may be followed for producing very low levels
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of nitrogen impurity.
[0380]
[0381] Example 17 Pre-pressurised container
[0382]
[0383] A typical apparatus for the generation of therapeutic foam according to
the invention, as disclosed in WO 00/72821-Al, is shown in Figure 14.
[0384] The canister has an aluminium wall (14.1), the inside surface of which
is
coated with an epoxy resin. The bottom of the canister (14.2) is domed inward.
The
canister inner chamber (14.4) is pre-purged with 100% oxygen for 1 minute,
containing 15 ml of a 1 % vol/vol polidocanol/20 mmol phosphate buffered
saline
solution/4% ethanol, then filled with the required gas mixture.
[0385] A standard 1 inch diameter EcosolTM aerosol valve (14.5)
(Precision Valve, Peterborough, UK) is crimped into the top of the canister
after
sterile part filling with the solution and may be activated by depressing an
actuator cap (14.6) to release content via an outlet nozzle (14.13) sized to
engage a
Luer fitting of a syringe or multi-way connector (not shown). A further
connector (14.7) locates on the bottom of the standard valve and mounts four
Nylon 66 meshes held in high density polyethylene (HDPE) rings (14.8), all
within an
open-ended polypropylene casing. These meshes have diameter of 6 mm and have
a 14% open area made up of 20 pm pores, with the meshes spaced 3.5 mm apart.
[0386] A further connector (14.9) locates on the bottom of the
connector holding the meshes and receives a housing (14.10) which mounts the
dip tube (14.12) and includes gas receiving holes (14.11 a, 14.11 b) which
admit gas
from chamber (14.4) into the flow of liquid which rises up the dip-tube on
operation of
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the actuator (14.6). These are conveniently defined by an EcosolTM device
provided by Precision Valve, Peterborough, UK, provided with an insert.
Holes (14.11 a, 14.11 b) have cross-sectional area such that the sum total
ratio of this to the cross-sectional area of the liquid control orifice at the
base of
the valve housing (at the top of the dip-tube) is controlled to provide the
required
gas/liquid ratio.
[0387]
[0388] Example 18 container with engaging means and mesh stack
shuttle
[0389) A device comprising a container provided with engaging means and a
mesh stack shuttle according to the invention, as disclosed in WO 02/41872-Al,
is shown in Figure 15. The device comprises a low pressure container (15.1)
for an
aqueous sclerosant liquid and an unreactive gas atmosphere, a container (15.2)
for a
physiologically acceptable blood-dispersible gas and an engaging means
comprising
a connector (15.3).
[0390] The container (15.2) for a physiologically acceptable blood-dispersible
gas is charged at 5.8 bar absolute pressure with the required gas mixture,
whereas
the container (15.1) is charged with an inert gas. Container (15.2) is used to
pressurise container (15.1) at the point of use to approx 3.5 bar absolute and
is then
discarded, just before the foam is required. The two containers will thus be
referred to hereinafter as the PD [polidocanol] can (15.1) and the 02 can
(15.2),
and the term "bi-can" will be used to refer to the concept of two containers.
[0391] Each of the cans (15.1, 15.2) is provided with a snap-fit
mounting (15.4, 15.5). These may be made as identical mouldings. The
snap-fit parts (15.4, 15.5) engage the crimped-on mounting cup (15.6, 15.7) of
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each can (15.1, 15.2) with high frictional force. The connector is made in
two halves (15.8, 15.9), and the high frictional force allows the user to grip
the
two connected cans (15.1, 15.2) and rotate the connector halves (15.8, 15.9)
relative to each other without slippage between connector (15.3) and cans.
Each
of these can mountings (15.6, 15.7) has snap-fit holes (15.10, 15.11) for
engaging mating prongs (15.12, 15.13) which are on the appropriate surfaces of
the two halves (15.8, 15.9) of the connector.
[0392] The connector (15.3) is an assembly comprising a number of
injection mouldings. The two halves (15.8, 15.9) of the connector are in the
form of
cam track sleeves which fit together as two concentric tubes. These tubes are
linked by proud pins (15.14) on one half that engage sunken cam tracks (15.15)
on
the other half. The cam tracks have three detented stop positions. The first
of these
detents is the stop position for storage. An extra security on this detent is
given by
placing a removable collar (15.16) in a gap between the end of one sleeve and
the
other. Until this collar (15.16) is removed it is not possible to rotate the
sleeves past
the first detent position. This ensures against accidental actuation of the
connector.
[0393] The cam track sleeves (15.8, 15.9) are injection moulded from
ABS as separate items, and are later assembled so that they engage one another
on
the first stop of the detented cam track. The assembled sleeves are snap-
fitted as a
unit onto the 02 can (15.2) mounting plate (15.5) via four locating prongs.
The
security collar is added at this point to make an 02 can subassembly.
[0394] The connector (15.3) includes in its interior a series of foaming
elements comprising a mesh stack shuttle (15.17) on the connector half (15.8)
adjacent to the PD can (15.1). The mesh stack shuttle (15.17) is comprised of
four injection moulded disk filters with mesh hole size of 20 pm and an open
area of
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approx. 14%, and two end fittings, suitable for leak-free connection to the
two canisters. These elements are pre-assembled and used as an insert in a
further injection moulding operation that encases them in an overmoulding
(15.18)
that provides a gas-tight seal around the meshes, and defines the outer
surfaces of
the mesh stack shuttle. The end fittings of the stack (15.17) are designed to
give
gas-tight face and/or rim seals against the stem valves (15.19, 15.20) of the
two cans (15.1, 15.2) to ensure sterility of gas transfer between the two
cans.
[0395] The mesh stack shuttle (15.17) is assembled onto the PD can
valve (15.19) by push-fitting the components together in a aseptic
environment.
[0396] The PD can (15.1) and attached shuttle (15.17) are offered up to the
connector (15.3) and the attached 02 can (15.2), and a sliding fit made to
allow snap-fitting of the four locating prongs (15.12) on the PD can side of
the
connector (15.3) into the mating holes (15.10) in the mounting plate (15.4) on
the
PD can (15.1). This completes the assembly of the system. In this state, there
is
around 2 mm of clearance between the stem valve (15.20) of the 02 can (15.2)
and
the point at which it will form a seal against a female Luer outlet from the
stack.
[0397] When the security collar (15.16) is removed, it is possible to grasp
the
two cans (15.1, 15.2) and rotate one half of the connector (15.3) against the
other half to engage and open the 02 can valve (15.20).
[0398] As the rotation of the connector (15.3) continues to its second
detent position, the PD can valve (15.19) opens fully. The gas flow from the
02 can
(15.2) is restricted by a small outlet hole (15.21) in the stem valve (15.20).
It takes
about 45 seconds at the second detent position for the gas pressure to
(almost)
equilibrate between the two cans to a level of 3.45 bar 0.15 bar.
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[0399] After the 45 second wait at the second detent position, the
connector (15.3) is rotated further to the third detent position by the user.
At this
position, the two cans (15.1, 15.2) can be separated, leaving the PD can
(15.1) with
half (15.8) of the connector and the shuttle assembly (15.17) captive between
the
connector and the PD can. The 02 can (15.2) is discarded at this point.
[0400] A standard 1 inch diameter aerosol valve (15.19) (Precision Valve,
Peterborough, UK) is crimped into the top of the PD can (15.1) before or after
sterile
filling with the solution and may be activated by depressing the mesh stack
shuttle (15.17), which functions as an aerosol valve actuator mechanism, to
release
the contents via an outlet nozzle (15.22) sized to engage a Luer fitting of a
syringe or
multi-way connector (not shown).
[0401]
[0402] Example 19: Study to assess the effect on physical
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properties of foam from changes to the mesh material in the mesh stack
[0403]
[0404] This study outlines the effect on foam properties of changing the
shuttle mesh pore size from 20 microns to 5 microns, in combination with
changes to the gas pressure and gas composition in the canister. The study
dates from before the inventors' realisation that a nitrogen concentration of
0.8 or below was desirable. Its main purpose was to test whether use of a
5micron instead of a 20micron mesh will compensate for eliminating the 25%
nitrogen which was previously deliberately incorporated into the polidocanol
canister. The "100%" carbon dioxide and "100 /x" oxygen referred to in this
and the following examples will in fact incorporate levels of nitrogen
impurity
and the final dual canister product discussed in these examples will probably
produce as foam of about 1-2% nitrogen impurity.
[0405] Two different gas compositions were used. In one, the canister
containing the 1 % polidocanol solution and a 75%/25% atmosphere of
C02/N2 is evacuated to 0.5 bar absolute pressure, whilst the other canister is
pressurised to 5.9 bar absolute with oxygen. In the other, the canister
containing the 1 % polidocanol solution is pressurised to 1.2 0.1 bar
absolute with 100% C02, whilst the other canister is pressurised to 5.8 0.1
bar absolute with oxygen.
[0406] The objective of the study is to examine and compare results
obtained using 5 micron and 20 micron shuttle meshes, for PD canister
pressures of 0.5 bar absolute with the current gas atmosphere and for 1.2 bar
absolute PD canister pressures with a 100% C02 as the filling gas.
[0407] Materials and Methods:
[0408] All sample preparation was performed in a laminar flow booth
keeping exposure times to atmosphere to a minimum.
[0409] Shuttle units containing a stack of 4 nylon 6/6 woven meshes of
6 mm diameter in a class 100K cleanroom moulding facility were used. They
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differ in the following aspects shown in Table 3 below.
[0410] Table 5. Physical characteristics of the 20 m and 5 m meshes
compare
Mesh Thickness Pore size Open Area (% area of Thread diameter
Type ( m) ( m) pores) ( m)
m 100 5 1 37
20 m 55 20 14 34
5
Bioreliance Ltd, Stirling, Scotland, U.K., made the 1% polidocanol solution
for the
study under controlled conditions to the formula in Table 4.
0411 Table 6. Composition of the 1 % polidocanol solution
Material Quantities
% W/W per 1000 g
Polidocanol 1.000 10.00 g
Ethanol 96% EP 4.200 42.00 g
Disodium Hydrogen Phosphate 0.240 2.40 g
Dihydrate. EP
Potassium Di-hydrogen Phosphate. EP 0.085 0.85 g
0.1 M Sodium Hydroxide Solution [used q.s. q.s.
for adjustment of pH: 7.2-7.5]
0.1 M Hydrochloric Acid q.s. q.s.
Water for injection. EP [used to adjust to approx. 94.475 q.s. to approx.
944.75g q.s.
final weight] 100.00% to 1000.00 g
TOTAL: 100.00% 1000.00 g
[0412] The polidocanol solution was sterile filtered using a 0.2-micron
filter before filling into clean glass screw top bottles.
[0413] Bi-can assemblies were prepared for testing to the
specifications of gas mix and pressure in the polidocanol canister detailed in
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Table 5.
[0414] Table 7. Summary of PD canister preparation for each treatment
group
Canister Sample Gas Gas Pressure Mesh Pore Size
Label Type Composition (bar absolute) ( m)
75% C02/25%
C Control 1 0.5 20
N2
75% C02/25%
D Test 1 0.5 5
N2
A Control 2 100% CO2 1.2 20
B Test 2 100% CO2 1.2 5
[0415] The order of testing of the experimental series was important, in
that changes in ambient laboratory temperature affect the half separation time
results. Experiments progressed cyclically through the sample types rather
than test all of one sample type, followed by all of another sample type. This
minimised the effect of any drift in laboratory temperature throughout the
experiments. The laboratory temperature was maintained as close to 20 C
as possible.
[0416] It was also essential that the temperature of the half separation
time apparatus be allowed to fully equilibrate to ambient room temperature
following cleaning and drying steps between successive experimental
measurements.
[0417] Summary of Tests:
[0418] The tests and specifications performed on the bi-can units in
this study are summarised in Table 6.
[0419] Table 8. Summary of tests and specifications
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TEST SPECIFICATION
1 Appearance of Device No corrosion of canisters or valves.
Free from signs of leakage and external damage
2 Gas Pressure 1.10 to 1.30 bar absolute for Type 2 samples
Polidocanol Canister 0.4 to 0.6 bar absolute for Type 1 samples
Oxygen Canister 4.90 to 5.9 bar absolute
3. Appearance of Foam Upon actuation, a white foam is produced. After the
foam has settled, a clear and colourless
liquid is observed.
4. pH of Solution 6.6 to 7.5
(collapsed foam)
Foam density 0.10 to 0.16 g/ml.
6 Foam Half Separation 150 to 240 seconds
Time
7 Bubble Size (Diameter
Distribution)
< 30 m < 20.0%
30 m to 280 m ? 75.0%
281 m to 500 m 5.0%
> 500 m None
8 Particulates (Visible) Complies with Ph. Eur.
and Sub-Visible)
9 Particulates (Sub- The collapsed foam contains not more than 1000
Visible) particles per ml >_ 10 m and not more than 100
particles >_ 25 m per ml.
Polidocanol GC pattern and retention times to be equivalent to
identification by GC reference preparation
method
11 Polidocanol Assay 0.90 to 1.10% w/w
12 Related Substances No single identified impurity >0.20% area.
No single unidentified impurity >0.10% area.
Total impurities < 4.0% area
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[0420] Results:
[0421] Results of the tests described in Table 6 on bi-cans prepared as
described in Table 5 are summarised in the following paragraphs.
[0422]
[0423] Appear of device and foam
[0424] In all cases the appearance of the devices conformed to
specification in that the device showed no corrosion of canisters or valves
and
were free from signs of leakage and external damage. Upon actuation of the
charged PD canister a white foam was produced. After the foam had settled,
a clear and colourless liquid was observed.
[0425]
[0426] Density, half separation time and pH
[0427] Foam from all devices conformed to density and half separation
time specification. However, one unexpectedly low result was obtained (C1
canister 1) but an additional two devices were tested which behaved as
expected. In spite of the low result, the average conformed to specification.
In
general, foam generated via the 5 ^m shuttles had longer half separation
times. Results are summarised in Table 7.
[0428]
[0429] The average pH of the foam generated conformed to
specification. However, foam produced from the 100% C02 canister were
close to the lower limit of detection of the specification and in one instance
(C2 canister 4) it was just below specification. Results summarised in Table
7.
[0430]
[0431] The gas pressure in the oxygen cans and the polidocanol cans
conformed to specification in all cases. In one instance (C1 canister 6) a
slightly lower oxygen canister pressure than expected was recorded. Results
are summarised here in Table 7.
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[0432]
[0433] Table 9. Table summarising the foam density, half separation
time, pH and canister gas pressures
Gas pressure
density half life (bars abs)
Test Condition (g/cm3) (see) pH Oxygen PD
Specification 0.10-0.16 150-240 6.6-7.5 4.9-5.9 0.4-0.6
100% C02, 1.2 Bar, 20 pm mesh
Canister Al 0.12 164 6.7 5.6 1.1
Canister A2 0.13 150 6.7 5.5 1.1
Canister A3 0.13 153 6.6 5.8 1.1
Canister A4 0.15 154 6.5 5.5 1.1
Canister A5 0.13 154 6.7 5.6 1.1
Canister A6 0.15 154 6.5 5.6 1.1
Average 0.13 155 6.6 5.6 1.1
100% C02,1.2 Bar, 5 m mesh
Canister B 1 0.12 182 6.6 5.4 1.1
Canister B2 0.12 169 6.7 5.6 1.1
Canister B3 0.14 162 6.6 5.4 1.1
Canister B4 0.1 173 6.7 5.7 1.1
Canister B5 0.12 168 6.6 5.6 1.1
Canister B6 0.15 161 6.5 5.4 1.1
Average 0.13 169 6.6 5.5 1.1
75% CO2/25% N2, 0.5 Bar, 20 pm mesh
Canister Cl 0.14 157# 6.9 5.4 0.6
Canister C2 0.15 182 6.9 5.5 0.6
Canister C3 0.13 193 6.9 5.4 0.6
Canister C4 0.15 183 6.9 5.7 0.6
Canister C5 0.15 192 6.8 5.6 0.5
Canister C6 0.15 191 6.9 5.0 0.6
Canister C11 0.14 189 7.0 5.7 0.6
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Canister C12 0.13 179 7.0 5.4 0.6
Average 0.14 183 6.9 5.5 0.6
75% C02/25% N2, 0.5 Bar, 5 m mesh
Canister D1 0.15 203 6.9 5.4 0.6
Canister D2 0.12 209 7.0 5.6 0.6
Canister D3 0.16 198 6.8 5.6 0.6
Canister D4 0.12 205 6.9 5.7 0.6
Canister D5 0.12 208 6.9 5.4 0.6
Canister D6 0.15 205 6.9 5.6 0.6
Average 0.14 205 6.9 5.6 0.6
[0434] Bubble size distribution:
[0435] The average bubble size for all conditions was within
specification with the exception of control 1 (C) where the >500 ^m which
averaged at one oversized bubble. Results are summarised here in Table 8.
[0436]
[0437] Table 10. Table to summarise the bubble size distribution of
foam generated
Bubble Diameters ( m)
<30 30-280 281-500 >500
Specification <=20% >=80% <=5% None
100% C02, 1.2 Bar, 20 m mesh
Canister Al 8.2% 89.5% 2.3% 0
Canister A2 8.1% 89.7% 2.2% 0
Canister A3 7.9% 85.3% 6.8% 0
Canister A4 9.0% 88.3% 2.6% 1
Canister A5 7.9% 90.7% 1.5% 0
Canister A6 11.0% 88.1% 0.9% 0
Average 8.7% 88.6% 2.7% 0
100% C02,1.2 Bar, 5 pm mesh
Canister B1 7.8% 91.8% 0.4% 0
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Canister B2 5.5% 94.2% 0.3% 0
Canister B3 8.6% 90.7% 0.7% 0
Canister B4 8.8% 91.1% 0.2% 0
Canister B5 7.7% 92.2% 0.0% 0
Canister B6 8.2% 91.3% 0.5% 0
Average 7.8% 91.9% 0.4% 0
75% CO2/25% N2, 0.5 Bar, 20 m mesh
Canister Cl 8.9% 87.2% 3.9% 0
Canister C2 10.0% 89.3% 0.6% 0
Canister C3 8.9% 86.5% 4.5% 1
Canister C4 9.7% 87.7% 2.5% 4
Canister C5 10.7% 87.9% 1.5% 0
Canister C6 10.1% 88.0% 1.9% 0
Canister C11 9.6% 89.5% 1.0% 0
Canister C12 11.0% 87.6% 1.4% 0
Average 9.7% 88.1% 2.5% 1.0
75% CO2/25% N2, 0.5 Bar, 5 m mesh
Canister D1 7.8% 92.0% 0.2% 0
Canister D2 8.1% 91.4% 0.6% 0
Canister D3 10.9% 89.0% 0.1% 0
Canister D4 8.5% 91.2% 0.2% 0
Canister D5 8.8% 91.1% 0.1% 0
Canister D6 10.2% 89.8% 0.0% 0
Average 9.0% 90.7% 0.2% 0
# Value from Control 1, canister 1 are not included in the average
[0438] Particulates (sub visible)
[0439] The collapsed foam from all canisters complied to specification
for particulates, in so far as there were no more than 1,000 particles/ml ? 10
pm and no more than 100 particles/ml ? 25 pm. Those which had 100% C02
gas mixture gave the lowest numbers of particles overall. There were no
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visible particles seen in the collapsed foam. The results are summarised here
in Table 7.
[0440] The appearance of foam from each device conformed to
specification. The appearance of all canisters conformed to specification.
[0441]
[0442] Table 11. Sub-visible particulates as per in house method MS14
Device No Counts per ml Counts per container (18 ml) Result
> 10 m > 10-25 m >25 m > 10 m > 10-25 m > 25 m
Ref A Can 7 281.6 271.4 10.2 5,069 4,885 184 Complies
Ref A Can 8 235.3 227.9 7.4 4,235 4,102 133 Complies
Ref B Can 7 112.8 109.8 3 2,030 1,976 54 Complies
Ref B Can 8 123.1 116.3 6.8 2,216 2,093 122 Complies
Ref C Can 7 386.1 370.2 15.9 6,950 6,664 286 Complies
Ref C Can 8 369.5 350.6 18.9 6,651 6,311 340 Complies
Ref D Can 7 130.2 123.5 6.7 2,344 2,223 121 Complies
Ref D Can 8 152.1 141.4 10.7 2,738 2,545 193 Complies
[0443] Polidocanol identification, assay and related substances
[0444] No significant differences were observed between the results of
the Control and Test preparations. All samples met all specifications for
related substances, assay value and identity.
[0445] Analysis of the samples using the 25 m column was undertaken,
but no significant peaks were observed relating to Nylon 6,6 interactions in
these samples.
[0446]
[0447] Example 20. Further study to assess the effect on physical
properties of foam from changes to the mesh material in the mesh stack
[0448]
[0449] The study of Example 9 was repeated using a device in which
the shuttle mesh pore size was 20 microns, 11 microns and 5 microns, in
combination with changes to the gas pressure and gas composition in the
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canister. Bi-can assemblies were prepared for testing to the specifications of
gas mix and pressure in the polidocanol canister detailed in Table 9.
[0450]
[0451 ] Table 12. Summary of PD canister preparation for each
treatment rou
Sample Gas Composition Gas Pressure Mesh Pore Size
Type (bar absolute) ( m)
Control 1 75%CO2/25% N2 0.5 20
Control 2 100% CO2 1.2 20
Test 2 100% CO2 1.2 5
Test 3 100% CO2 1.2 11
[0452] Various batches of the foam resulting from the test in which the
shuttle mesh pore size was 11 microns had the following characteristics:
[0453]
[0454] Table 13 (a). Bubble Diameter (micrometers)
<= 30 > 30 - 280 > 280 - 500 > 500
9.2% 90.2% 0.6% 0.0%
11.8% 88.2% 0.0% 0.0%
10.6% 89.4% 0.0% 0.0%
10.2% 89.8% 0.0% 0.0%
10.6% 89.1% 0.3% 0.0%
10.5% 89.4% 0.1% 0.0%
Table 13 (b). Bubble Diameter (micrometers) excluding below 30 m
< 30 -130 > 30 - 280 > 280 - 500 > 500
59.1% 99.4% 0.6% 0.0%
71.2% 100.0% 0.0% 0.0%
75.3% 100.0% 0.0% 0.0%
67.3% 100.0% 0.0% 0.0%
66.4% 99.7% 0.3% 0.0%
73.6% 99.9% 0.1% 0.0%
Table 14. Density and Half Life
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Density (g/cm3) Half Life in
0.12 180 sec
0.14 171 sec
0.14 175 sec
0.12 175 sec
0.13 177 sec
0.15 177 sec
[0455]
[0456] Example 21
19
[0457]
[0458] Experiments were conducted to compare the physical properties
of sclerosing foam made by the methods of Cabrera, using a range of
C02/02 gas mixtures as the ambient atmosphere in which a small brush is
rotated at high speed to whip polidocanol (PD) solution into a foam, as
disclosed in EP 0656203.
[0459] All sample preparation was performed under controlled
laboratory conditions at temperatures within the range 18-22 degrees C,
using polidocanol solution obtained from Kreussler 1 % Aethoxysclerol. The
container was a 100ml beaker. The beaker and the 1 Oml of solution was
placed in a small glass aquarium tank which was modified to allow the
internal space to be sealed from atmosphere, then flushed and flooded with
the test gas mix.
[0460] During the experiments, a small ingress of the test gas mix was
present to ensure that atmospheric nitrogen and oxygen cannot enter the
glass tank and change the known gas mix. A flexible drive shaft was
attached to the micromotor to allow the micromotor to stay outside of the
glass tank, whilst driving the brush inside the glass tank at the required
speed. Where the flexible drive shaft entered the glass tank, it was sealed to
avoid leaks from atmosphere
[0461 ] The flushing of the glass tank was performed for 30 seconds
with the gas mix supplied at 0.2 bar above atmospheric pressure to the glass
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tank. After the 30 second flush, the regulator was turned down to allow a
trickle of ingressing gas for the rest of the experiment. The speed of
rotation
and duration of whipping was fixed at 11500 rpm and 90 seconds.
[0462] The results in Table 15 show the density and half life of foams
made with 100% C02, 100% 02, 75% C02/25%02 and air. For each gas,
foams were made with plain polidocanol, polidocanol and 5% glycerol,
polidocanol and 25% glycerol and polidocanol and 40% glycerol. Two runs
are reported (1 and 2) for each foam. The results show that higher
percentages of glycerol enable one to make a C02 foam with adequate
density and half life.
[0463]
Table 15(a) Air
Density and Half Separation Time
Density /ml Half Life Sec
Plain PD air 1 0.16 173
Plain PD air 2 0.17 170
5% glycerol 1 0.20 188
5% glycerol 2 0.20 195
25% glycerol 1 0.30 539
25% glycerol 2 0.27 535
40% glycerol 1 0.44 459
40% glycerol 2 0.45 575
Table 15(b) 100% 02
Density and Half Separation Time
Density /ml Half Life Sec
Plain PD 02 1 0.18 122
Plain PD 02 2 0.17 120
025CA 0.18 144
025GB 0.18 140
0225ga 0.30 343
0225gb 0.34 429
0240ga 0.47 432
0240gb 0.44 525
Table 15(c) 75% C02 / 25% 02
Density and Half Separation Time
Density ml Half Life sec
2575 plain PD 1 0.20 72
2575 plain PD 2 0.18 78
2575 5%G A 0.16 81
2576 5%G B 0.19 82
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2575 25% G A 0.33 216
2576 25% G B 0.29 229
2575 40% G A 0.46 399
2576 40% G B 0.47 410
Table 15 (d)100& C02
Density and Half Separation Time
Density /ml Half Life Min
Plain PD C02 1 0.19 55
Plain PD C02 2 0.19 71
CO25GA 0.24 57
CO25GB 0.20 66
C0225ga 0.29 187
C0225gb 0.33 239
co240ga 0.48 227
co240gb 0.51 273
[0464]
[0465] Example 22: Polidocanol, glycerol and C02 foams
[0466]
[0467] Foams were made with polidocanol, glycerol and C02 using
various techniques. The technique used to make the foam plays an important
role in the half life and density of the resulting foam.
[0468]
[0469] Double Syringe technique
[0470] 500ml of a buffered solution of 1 % polidocanol and 30% glycerol
was made up using the following procedure.
[0471] 100% polidocanol (pd) - a waxy solid - was melted by placing
in a bath of warm water
[0472] 100ml distilled water was weighed out in a 1000ml beaker
[0473] 0.425g potassium dihydrogen phosphate was added as a
stabiliser
[0474] 5g of the liquefied pd was weighed out
[0475] 21 g of 96% ethanol was weighed out
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[0476] The ethanol and pd were mixed, then added to distilled water
[0477] 150g glycerol was added
[0478] Water was added to the 425m1 mark
[0479] pH was adjusted by adding 0.1 M sodium hydroxide to between
7.34 and 7.38 pH.
[0480] Distilled water was added to make up to 500g on scale
[0481] The solution was filtered through a 0.25micron filter.
[0482] The same procedure was followed, with an increased amount of
glycerol, to make the 40% glycerol solution.
[0483] Into a 50m1 glass syringe was drawn 1 Oml of the pd/glycerol
solution. The nozzle of another 50ml glass syringe was connected to a line
from a cylinder of carbon dioxide (B.O.C. "CP grade" having a purity level of
99.995%). The syringe was filled with carbon dioxide and then removed from
the line, the plunger depressed and the syringe then re-filled to the 50ml
graduation on the syringe barrel and then detached from the line. A
connector having a female luer at each end and a through bore of diameter
approximately 1 mm was then connected to the line and flushed through. The
two syringes were then each connected to the connector device.
[0484] The carbon dioxide and pd/glycerol solution were then manually
pumped back and forth between the two syringes as fast as possible for in
excess of 30 cycles. A foam formed in the syringes during this process. After
the final cycle, the foam was quickly transferred to half-life and density
measuring apparatus and the half life and density of the foam determined.
[0485] The procedure was carried out for a buffered solution of 1 %
polidocanol and 30% glycerol and for a buffered solution of 1 % polidocanol
and 40% glycerol.
[0486] In each case the resulting foam was observed to be somewhat
runny, though not like a liquid. It would form very flat, gently rounded
"blob"
on a surface which decayed and ran away as liquid within five seconds.
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[0487]
[0488] Double syringe and mesh technique
[0489] The procedure outline above for the double syringe technique
was followed, with the following variations.
[0490] Instead of using a connector with a 1 mm bore, a so called
"mesh stack" device was prepared having a flow path which incorporated a
series of four mesh elements. Each mesh element measured about 2-3mm in
diameter and had pores with diameter 5 micron. At each end of the device
was a luer connection.
[0491] The syringes were again cycled as fast as possible but this was
considerably slower than was possible with the simple connector having a
1 mm bore. After 10 cycles the pumping of the syringes was stopped since no
further changes in the foam could be observed. Two operators were
necessary to perform this cycling, each operator depressing the plunger on a
respective syringe.
[0492] The procedure was carried out for a buffered solution of 1 %
polidocanol and 30% glycerol and for a buffered solution of 1 % polidocanol
and 40% glycerol.
[0493] The appearance of the foams made with the double syringe and
mesh stack technique was quite similar to those produced with the double
syringe style technique; however the "blobs" were less flat and took
somewhat longer to decay.
[0494]
[0495] Canister techinque
[0496] Pressurised canisters with a capacity of approximately 100ml
were made up with about 20ml of buffered polidocanol/glycerol solution. The
canisters were then pressurised with substantially pure carbon dioxide to a
pressure of 3.5bar absolute.
[0497] The canisters are each fitted with a valve, with a dip tube
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extending from the valve to the base of the canister. On each side of the
valve are apertures which draw in gas as liquid passes up the dup tube under
pressure. Above the valve, each canister is fitted with a mesh stack unit as
described above.
[0498] To dispense foam, the canister valve is opened. The first
portion of foam is discarded and then foam is dispensed directly into the half
life and density measurement apparatus.
[0499] The procedure was carried out with canisters containing a
buffered solution of 1 % polidocanol and 30% glycerol and with canisters
containing a buffered solution of 1 % polidocanol and 40% glycerol.
[0500] The foam produced by the 30% glycerol solution was relatively
stiff and formed a compact, rounded blob on a surface. The blob could be
seen to start decaying within a few seconds, but remained as a blob rather
than a liquid puddle for much longer. Observations were not recorded for the
40% glycerol.
[0501 ] Results
[0502] Double Syringe Foam
[0503] 1) (100 % C02, 1 % polidocanol, 30% glycerol)
[0504] Density = 0.231; Half life = 99 secs
[0505] 2) (100 % CO2, 1 % polidocanol, 40% glycerol)
[0506] Unable to make sufficient amount of foam
[0507] Double syringe and mesh technique
[0508] 1) (100 % C02, 1 % polidocanol, 30% glycerol)
[0509] Density=0.174; Half life = 155 secs
[0510] 2) (100 % C02, 1 % polidocanol, 40% glycerol)
[0511] Density=0.186; Half life = 166 secs
[0512] Canister
[0513] 1) (100 % C02, 1 % polidocanol, 30% glycerol)
[0514] Density = 0.094; Half life = 121 secs
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[0515] 2) (100 % C02, 1 % polidocanol, 30% glycerol)
[0516] Density=0.124; Half life = 166 secs
[0517] 3) (100 % C02, 1 % polidocanol, 30% glycerol)
[0518] Density=0.124; Half life = 108 secs
[0519]
[0520] Example 23: Polidocanol, glycerol and C02 foams
[0521]
[0522] The effects of different viscosity enhancing agents (glycerol,
PVP and ethanol) on the viscosity of the liquid phase before producing a foam
were examined. Viscosity was determined at 23oC using the Brookfield
device described above.
[0523] The effects of additional components on the density and half life
of C02 foams made using the methods of Cabrerra was also studied. Foams
were prepared using the polidocanol (PD) and different percentages of
viscosity enhancing agents (wtlwt) and the Cabrerra method described
above. The half life and density of the resulting foam was determined as
described above. Similar experiments can be used to determine if a
particular combination of viscosity enhancing agent, sclerosing agent, and
gas provide a foam with a suitable half-life and density. Foams were also
produced using a canister as described above and the results are presented
in Table 16.
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Table 16: Canister C02/glycerol results
Composition Density Half life Average Average Viscosity
(all compositions (g/ml) (seconds) Density Half life of Liquid
are 100% C02 & (g/ml) (seconds) Component
1% polidocanol) (cP)
5% glycerol 0.105 76
5% glycerol 0.109 58
5% glycerol 0.111 60 0.112 63 1.5
5% glycerol 0.117 59
5% glycerol 0.121 61
10% glycerol 0.112 78
10% glycerol 0.115 75 0.117 76 1.6
10% glycerol 0.118 78
10% glycerol 0.124 73
20% glycerol 0.113 92
20% glycerol 0.113 99
20% glycerol 0.113 104 0.115 96 2.2
20% glycerol 0.120 95
20% glycerol 0.114 90
25% glycerol 0.105 111
25% glycerol 0.106 109
25% glycerol 0.108 109 0.109 111 2.6
25% glycerol 0.109 118
25% glycerol 0.115 106
30% glycerol 0.094 121
30% glycerol 0.124 166 0.114 132 -
30% glycerol 0.124 108
40% glycerol 0.083 172
40% glycerol 0.133 174 0.118 173 -
40% glycerol 0.137 174
1% PVP C30 0.091 73
1% PVP C30 0.107 62 0.107 67 1.6
1% PVP C30 0.111 69
1% PVP C30 0.119 64
2% PVP C30 0.102 70
2% PVP C30 0.105 69 0.107 68 2.0
2% PVP C30 0.106 69
2% PVP C30 0.114 63
1 % PVP K90 0.068 142
1 % PVP K90 0.071 118
1% PVP K90 0.072 129 0.073 135 5.0
1% PVP K90 0.074 159
1% PVP K90 0.078 129
[0524]
